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9 Dielectric Relaxation, Part 2

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Choi asses in polymer dynamic based on
George Phillies book phenomenology of polymer solution dynamics Cambridge University Press 2011 ends today this
lecture E is lecture mind more
dielectric relaxation I'm
professor Phil is and this is part 2 of my classes on dielectric increment polymer solutions based on my book phenomenology ,comma dynamics Our OK so what we are going to do today is to continue with the reading of Chapter 7 all have homework again next time the issue was his fault dielectric spectroscopy is an enormously effective tool that gives us a wide variety of different measurements about Paul introduced here but we have lot of changes to the it has a few feature enhanced and ended on the vectors starts at 1 of the chain the points story to the other and that's a measurement of how big Paul reasoned solution it's not the only measure but it is a furthermore the union's dielectric relaxation spectra process to characterize the relaxation of this factor that is as time goes on the little settlements along chain all perform Brownian motion the diffuse now they have to stay attached to each other's aid views so they can just move randomly completely but of the chain starts in this configuration after a while 2 sorts of 3 sorts of things with him number 1 on the side of massive change which is originally here Saiful number 2 the 2 chains ends will have moved and marking to change hands relative to to each other and therefore the ends and factory change length and direction and number 3 in the 1st of exchange between me and will change which way .period now the details of how it change how it translates and rotates the changes shape our quite complicated and not shown that sketch furthermore there are a number of entirely contradictory theoretical models for how polymer chains movements the key feature here is from the standpoint of dielectric spectroscopy if we have to change whose pieces all asymmetric so each piece has a little people what a lined up along the polymer chain the resolve of all of these little by Poles lined up is that the Paul McShane has a dipole moment which points from 1 end of the Polish aimed the other in the and what dielectric relaxation that crossed the median measurement the dielectric instrument used in terms of what the average length of these things after all have a chance give the change the relaxation this time the line and the direction that is as time goes on the direction fluctuates white fluctuates it's geared fluctuate 1 available longtime another value knowledge and this relaxation in the direction gives us after peace theoretical work the frequency dependence of the dielectric response all their minds said dielectric constant is a former New estimated dimensions and I went off mentally away the wrong direction the question the answer you were looking forward to what units are you with and answer is that this the right to be electrical attended potential energy between 2 charges that form we are in CDs yes movements epsilon is 1 of the things that you the made found the war in the wild in a lot of this is frequency stay around 80 years so in water and epsilon has dimensions however most of you were probably more used to onside units in which case there have .period caps along marked down here in the back and pile an extra constant or change absence of mountain Absalon and that's SI units of electrostatic submits charges and who wants and then case Exelon was no longer he wants a number from Poland because they the important issues of the dielectric constant in water is much higher than it is in the vacuum because of water if you find electric field that light up all the little water molecules least bit on if you think for a moment school chief compliant picking off the electric field don't want more completely than don't they don't stop getting in Greece and the dielectric came from and that's correct stuff you actually trying applied electric field like that externally or you will have an entertaining time with your experimental efforts
on the other hand if you the water and drop into the sales sodium ions which alright someplace this is a lot of charges very tiny and there is being left the field here and the water molecules very near sodium ions are very much a lineup so the such surrounding ions in the water but there is a shell where water molecules that pretty well lined up in the back .period since the basically already completed New Line baby he basically likened oil and their dielectric there is you get some increase the dielectric constant because you move the electron shells around but basically you get the water molecules there already lined up by by local OK let us go back to here and what I was saying is you can measure different sorts of things about a of followers the next thing you can do is just say people supposedly have more than 1 thing at the same time but where it came there is another change what happened 50 years ago this was a major literature dispute there were no very easy ways to measure all you know roughly how they call chain was booked question is if you increased polymer concentration what happened and what the answer is if you really run out the the concentration chains shrinking on but don't from it's not quite clear that if you turn up the volume of trade the changes do strange things but they also spent a lot of time penetrating on his books that leads to the obvious question lightly into penetrate like child can well this trip we have a call chains In his song typical size it matters bit which the method you used to characterize the typical size because it's a random structure and it's not a solid body but our our noses as molecular weight power around half of soldiers not quite . 6 yeah now suppose you have an object whose radius grows as the half wore a bit more power of molecular weight that means the molecular weight of the object is proportional to our square or maybe it less and so you have an object whose molecular weight roses square of the have you seen an object like that work yes it's a spherical shell if you have a spherical shell the masses proportional to the surface area yesterday they have there is less proportional to service of course polymers are not spherical shells but they have the same properties serial Chelsea namely if you increase the main the object has to get bigger fairly large big bigger fairly quickly I should say and through the hysterical shell is mostly empty spaces note :colon changed the color story and runs around all inside this what were called worries however that as I increased the molecular weight of follows this Parliament gets bigger and bigger and it still hasn't happened history shall then we find mentioned running a line through it on the average I hit the ball well flights so far I haven't really been told that it's really big radius underlined through it I only had a tiny hole in prosperity cross-section all replaced most of this is empty space and polymers can then interplanetary and that's what they do now will take on the books in advance to figure this out .period war and terrorism to and I grabbed the wrong thing this morning but I'm fairly sure 7 . 4 he's heptane solutions of 114 743 billable Polly yes OK very good and what is the point of this well the 1st issue is what kind of vertical axis is valid Absalon overseas Delta Epsilon is change in the dielectric constant there some constants in all of the solution as you add more polymer well-documented more polymer each molecule makes its contribution to the dielectric constant but if you divide out if you
divide out the concentration of what is left is the dielectric increment from all of and dielectric increment from all over the world is approximately 4 were told about his constant in all this mean square seismology so let us start figure and you have a comparison there and as you make the molecule larger square gets larger because the chain is long and therefore madam where gets larger and therefore the dielectric increment gets larger and therefore if you stay at the top of concentration equals 0 left axes the larger molecule digital larger dielectric Inc now the next thing you can do is to increase the concentration of molecules and if you do that there's 1 thing you might need to worry about that is supposed to put a lot of molecules in a solution so here is called molecules and here is another column molecules a somewhat wrapped around each other the 1 thing that might just as well are those of shame is independent of each other and the reason you would worry about this is that if you packed the chains and the chain's lineup for example parallel to each of the dielectric increment of a lot of change is not linear and how many there there it's some larger number but the answer is here is the 1st thing that I do an air bridge over the solution the 2nd change would run through this way toward could run through in the opposite direction have hands and factory pointed opposite Lee and these 2 cases are essentially equally likely to occur in 2 states have about the same free energy and because the 2 states have the same free energy all the direction of this factor and the direction of that fact you're completely independent from each other and so when we look at the dielectric increment of a concentrated solution we're just seeing this very good approximation the single change behavior now there is deception today there is an
exception to that and the accession bearers of their molecules that you of concentration and they themselves a phased transition to liquid crystal In which case the molecules straightened out approximately they tend to think perhaps for all .period parallel ran parallel on on-site parallel there's a bunch of interesting phenomena here the outside this course in this case if you the concentration of suddenly there's very dramatic change in the dielectric which we are going to talk about so what happens if we increase concentration on the point of this discussion I just gave you is that this relationship between the dielectric environment and the mean square size of polymer chain does not care about the polymer concentration has sold a plot telecasts on overseas Brazil's Paul concentration by an essentially seeing the single change behavior I am seeing that good approximation and what do I see happen well if you look at 7 4 as I am run polymer concentration the dielectric increment of the single-chamber faults and there to bigger change the dielectric increment falls and it falls faster so that local concentrations With introducing molecular weight dielectric incremental increases but at higher concentrations these curves can cross and with the increasing volume of molecular weight the dielectric increment of the system is less what does this mean it means the very large Shane at high concentrations has contracted Donald they have now its size has gone increased considerably and its ability the increase in the on dielectric constant the solution has been substantially reduced so that is figure 7 . 4 few years to 7 . 4 B and C B is the big 1 of the bombs show slightly different effect which is also important but shows in the fact that as of Saturday visit class experiment said that as of Saturday physical and what what is stronger those figures as we take him home a change general experiment has its faults we have a polymer chains which were interested in we put it in a solution of all the chains such as Kroger Algeria's matrix and we choose the matrix polymer so the experimental technique doesn't see it so from the standpoint of our experimental technique we're looking at a probe although there is a solution out here the solution of well actually does contribute very high frequencies I liked but the solution is basically in their dielectric optically or whatever and we only see the approaching chains that you might ask how can you do this home and dielectric relaxation of go back to what we were saying about last lecture about how the polymer contributes at low frequencies the dielectric constant following a reviews have low frequencies to the dielectric constant if it as a result of its molecular structure along little balls inside the diagonals are arranged so they affixed to lie along the backbone of the poll for example this is a polyester the important feature here is this is the real key unit the 2 ends of the repeat units are different from each other and furthermore structure in the middle not give me any way to get marriages and trees so this has a dipole moment which lies along the pond Axis 1 way or the other on the other hand suppose I told underwritings through the use here is actually there has polyethylene oxide well polyethylene oxide young like routine Unit repeats that through repeated flying that it's the same with the unit and so there is a center of reflection and there's no net died long bond axis so this material does not contribute to the dielectric constant and if we stirred into the solution we get no effect of the dielectric behavior have to be a little careful of that statement because this is replacing your soul and just as the solvent a dielectric increment assignment most frequencies freed approximation so this and so you have to pay little attention to the fact that even tho this doesn't have big dipole moment you're doing a little bit of something to think about the case nonetheless here's a pro years a in matrix and we are now looking at what currently Freedom Tower the
current system so that system have crawled over things you hear matrix which in this case is also called and and if you are looking at she the behavior of the problem is you put Paul into the solution now why would you want to probe matrix fare as opposed to just stirring Paul Marie after all you're going to see the same in this experimental technique no matter where you have a trace pro-war high concentration all the experimental method gives you something close to single behavior the reason do this is matrix has followed a molecular weight on the program has fallen like away he and if you didn't species I can varied P S & L separate from each other that's very useful if you look back at 7 . were a notice that the small the contract slowly With increasing comes with the baseball and starts out that Centrex very fast With increasing concentration the solid lines by the way was the data points the figure all lines solid lines 1st French tests for their annual I call it the ball rolling the following lines are stretched exponential the smooth curves if you plant them on 17 paper we don't quite get straight lines out on the issue is the others OK so makes chains together they and big chains transformed little change but we come to the key question is the statement big chains shrank more than a little changes occurring because this is being and transformed or is it a courier because a very dangerous more effective causing approach to shrink no matter how the appropriate the question is the end of the year that percentage of traditional kiss that this large chain missions and the size was larger than analysts chance the little other than but if you 7 . forays Delta Epsilon oversee Delta Epsilon is proportional to to the meetings where but if you consider that you find it the smaller chain which is a 140 killer Gulten Polly I Supreme while we dropped the Delta Epsilon oversee these units from about 0 . 1 8 to about 0 . 1 4 which is it 20 percent sort of removing more for a large chain the arts 743 killed the shrinkage in queries from . 2 2 2 at a much lower concentration openly longed for which is a much larger fractional change I'm looking at 7 . 4 and therefore the larger chain fractionally it's actually contracting now you have to do you have to to do so said there and do some arithmetic if you want calculate with the change in the length as opposed to the fractional changing the length is all but the answer I think is a big change really but isn't that the big change is just more sensitive and compresses more words of the surrounding changes are bigger and are more effective and contracting and the 1st step to understanding that Ternary probate sold experiments such as the experiments you see in figures B and C. figure be shows on the 140 killer Dalton over and you know this well and pointed out there is series of curves this is the net as used leave this way what is happening is Europe increasing the size of the Matrix Paul and therefore a larger matrix fall is more effective that come at from that sea yeah part of a larger matrix polymer is more effective at compressing neighbouring chains than small matrix Paul although not in contrast will not really contrasts the same effect if you go to see which is a large chain and you ask what happens as you increase the major size you see the same behavior that is as you increase the matrix size I'll explain the significance of that 2nd there's more compression of the chain being Missouri now I would point out in although I suppose I him they also polymers that a certain concentration very low and suppose I increased the molecular weight assigned to increase the molecular weight he and goes off the radius goes up the radius roses and to one-half so what happens at low concentrations to the the density of polymer inside called oils I increased the molecular weight but the the density of polymer inside parliament was not the solution as old as determined by the concentration but inside a single
coil the density of actual change inside the oil is the ratio of the molecular weight to the volume of the change which is the molecular weight to a radius you which is the molecular weight polyester hard work and on the Darfur and the old . 6 so this is end of the 1 . 5 different ones .period 80 and therefore the density of polymer inside its own self is proportional to the threat withstand the minus column .period 5 were down to minus 4 . per ,comma between this is the behavior you would get in the face this or very close to what get in goods sold them all all going 6 yeah apart from Portugal and Greece seeks good is slightly overstated but you can also get solvents that In between these 2 many of the important issue I want to make is that as you make point were larger and larger density inside the coil gets smaller and smaller and therefore the same number of grams of polymer at low concentrations occupies more and more space is a molecular weight is injuries and lost if we have a solution some concentration the bigger the molecular weight the closer to the chains to Robin shoulders with each other and rubbing shoulders is about right because we're talking about the radius chain reflect this OK so let's figure 7 . 4 all the other things we can talk about if you want to ask how effective the aura matrix chains at compressing solvent compresses Paul train last look at the figures the next figure is 7 . 5 and it gives us a plot of said what is wrong with this against matrix molecular weight and I remind you of the notion is that Oreste where which is the same of units that .period help epsilon received it's like constant even -minus grows and growers constant that describes how steep the stretched exponential it's quite plotted this as a function of matrix molecular weight and there are 2 things you should know this the 1st is road doesn't it there I would not want to do too much emphasis on the last hole .period which indicates that might occur back very large molecular weight it's possible but there's only 1 data point there you really don't want extrapolate based on 1 data point that's a little dangerous the other thing that happens there are actually 2 curves there and the 2 Koreas show the 140 and 714 please tell us all the throat and so the answer is the larger probe has a larger role and must anthrax faster in some sense a small group of and furthermore Rose said is larger for the large growth than from the small rooms at all molecular weights and therefore what we can say yes there's a contraction and part of that is the difference between these 2 lines so part of it is that large chains are easier to compress after all there's a certain sense more and more hollow inside and also the case that if you increase the matrix molecular at there is a dramatic change in growth meaning big chains are more effective compressing each other and small chains so that is how works Monday there's something else that can be done at the analysis in Figure 7 . 6 could be carried out on the steps and with 7 . 6 dollars to say while we have all the properties different properties and weak in comparison and this these are results of From were color at all and what they did is to measure to the rules are there for the outside always read all of them out loud but they are there and the 1st thing they need is to measure the viscosity the measure staff relative to some of Scots after all of change the soul of the viscosity of the solution does change but it's not changing because Paul from and what they observed as a series of terrorist viscosity versus concentrations and with increasing polymer molecular weight only 1 ball solutions firings system will have with increasing following molecular weight of what happens is the viscosity of the solution goes up so if you have a solution the bigger the chain is the more visitors solution and that is a nice uniform however they that take this stuff and they do vitamin experiment binary solution and Ternary solution and they determined Powell the relaxation and what the relaxation time tells you is how long it takes for the pall of oil at the end
vector gap which way it was .period so if we have a technical polymer that has an effect on my arm as
time goes on the vector gets smaller and shorter and points in different directions and eventually the ball initial direction of polymer and that has nothing to do with the final direction and the 2 directions independent from each other as if you wait long enough yes originally the and and vector .period displayed direction my arms pointing but if I wait long enough the end and vector is equally likely to be pointing in every direction well invite increased follower concentration it takes longer for the analysts and defected to reorient change I'm not telling you how it reorient does reorient its proven by this experiment and therefore increased polymer concentration all that's the horizontal axis the invasion time goes on and you can now do binary experiments or return the experiment you can look at all the home following a change in solution with itself or you can look at the polymer In a solution with the matrix the quality of services will increase the matrix like the plague I was there to families of courage and 7 . 6 B and as I increased the matrix molecular weight even at very high concentrations Part B reorientation slows down so the molecular weight of the matrix has a direct effect on how fast the polymer oils and yeah but this result is although possibly not be fully consistent with all theories polymer dynamics all theories about homers solution I however you can always say Well the concentration isn't high enough the people molecular weight of matrix this isn't high enough and therefore isn't the theories some particular theory is wrong is that it's cute it's really not applicable to the solution OK the note which it had we're going to reach 7 . 3 but change the 2 Shane dimensions ,comma were actually going to talk about all the techniques be used to make a changes and this is 1 of the sections that was well too little too short for a chapter by itself so you sensible question where do put it and if the answer is there were lots of sensible places it could have been placed many people would have put it earlier chapters discussing Dion solution behavior the basic question we're talking about here is we have almost all of all it has a molecular weight and it has some characteristics size there are lots of ways character is the size problem and all however you define it is worth and some of the reasons why you're interested in this question is actually an analytical chemist request that is you have people sitting there in of the industrial chemical plant going Kupcho chunk or whatever turning out ,comma and he would like to characterize the Apollo so you know what the molecular weight of material you're making the reason for this is the large numbers of industrial applications all others many of them are sensitive to some particular property of all such as its molecular weight and you would like to know how big the polymer is because the customer may be paying for particularly molecular weight be awaited those show I'll work something like this and so what you do what you historically is you take the ball coming out of place the polymer coming out of the plan may be a solid word melts or very concentrated solution but no what and you take this the almost certainly are not producing dial you could be a dilute solution that tends to be inconvenient on an industrial scale that you have a favorite concentrations and take this material will lay out what you do is you take a bit of it and you die the reason you Is once it startled ,comma change here and there ,comma change there polishing here and on the average the changes quite separated from each other and because the separated from each other but these polymer chains change the behavior of the solution but they do so in a way that is not affected by the interactions trust determine if your lucky by how big chain and so you measure dilute solution properties and the diluted solution properties can be used to tell you how big the Paul Maritz man might sensibly Haskell what kind solution properties are and what about those solutions property is viscosity which is proportional to the viscosity of solvent long-lost constant as the concentration policy but if you just add little change didn't change the solution the linear term is quite completely accurate and the feature here is the kid who the book is an hourlong is this is this is a power series however you measure came along quite accurately and long is approximately proportional to some power my view of the size of the policy now I put a subscript of this is that this film match rating is the rating is inferred by asking how effective are these chains that changing the viscosity of the solution the reason that I will bring up of say this is this so battery radio is that there several other techniques for measuring polymer science for example this think solutions and shine a light beam we now use a laser stated promised that the 1st of the year upwards the solution is scary .period becomes cloudy all the lessons and reasonable solution because clouding will Poland changed and so on and not have the same index of refraction of water dollars so they scatter like and if you measure the intensity
of their life as a function of the angle .period as a function of angle while Parma chain is very small and it scares like effectively in all directions I'm skipping a light polarization issue which is experimentally very important all buddies vertical polarization in vertical polarization out scattering flaming horizontal so when looking down from fall of light scattering like this and colorization factors might be your paper if I can make a statement of the molecules very small areas like equally in all directions it however if we make a lot more vigorous eventually molecules starts to approach the incomparable the wavelength of light is likely to be passed and as a result this far more fuel is being eliminated by this part of the wave has long phase this part of of all of them is being illuminated by a different part of the lightwave and scatters light with a different face a light scattered from these 2 points can interfere I'm omitting details and as a result the life of area the depends on the scattering How is it depends scaring anymore as you make the polymer bigger and bigger make Poland bigger and bigger scattered light scattering focused more and more of forward direction the extreme case this in a sense as shown by the window glass if you bake polymer numerous so that you have a lot and it's only 1 molecule the laser beam goes straight through there if you wanna say the scattering it's only in exactly the forward direction and of the block homogeneous there's almost no scaring the sign all the objects is transparent a similar mathematical effect except it's not polymer is seen with no bullets but no less is transparent because to the extent you get scary world so you say scaring the scattering versus annual depends on polymer on the polymer molecular weight therefore were there is another radius and the other radius we can infer is determined by the scattering experiment I can round out a series of these and there are a series of different ways we can physically measure an apparent radius of wallet for example we could measure the diffusion coefficient how fast individual chamber and the diffusion coefficient he is proportional to the foreign line and on our we could do and lost my pressure measurement I will give it a go into that so we have a bunch of different ways we can make do with measurement and for each of them will have to ask working on some power and unjust solution power depends on solving it's a little less shade under 0 . 6 goods sold it's all . 5 and later sold the same numbers I don't want to go however most experimental techniques give the same number of is most experimental technique if you ask how does the of scattering power out as the on experiments have long molecular weight you turn out to get the same solved the 1 exception what is that if you do light-scattering measurements under some conditions you get a slightly different experts now so long as you know know what you're doing and they're using the same technique you need to know what the export and it's worth very nice areas Kansas Power true we determine what the powers we think some property by consul in Holland and manager a series of different followers of different molecular weight different ways to determine all the molecular weight having not missed a lot lot came his long enough and we get out of its power along the New Straits Times on well if any is proportional and it was this is proportional to to the new hello on the slope near the slope the line gives us the export through London compliance shall be modest challenge is that if you want to determine this fall this lumber and this proposed change by a significant amount and therefore if you say I would like to get a slope accurately well worth depends how accurately measured OK if you can't measure carried an incredibly accurately you can determine the with a fairly short pieces 1 problem is that they going to the clear and just look at the little boxes assault would be best for all of them maybe the slope as more life that maybe it's more like that and if you don't you cover much range this way or that way relative to the scaring your points you can't tell accurately with the slope so what you need to do is have something hovers ideally orders management here and fewer tours of Maryland there and then can make things work I think if you look at the long Chester you will serve the people that synthetic polymers with molecular weights up to about 15 million 15 million is a hero at the molecular weight to synthesize but except for biopolymers DNA is that 250 million is extremely costly in which the of a yes vote yes you can get extremely high molecular weights however if you go to a standard industrial catalogs and what policies the selling you will find their in the tens of thousands and left hundreds of thousands and maybe a shade over a million if you want something that is a 48 million dolphins and that is finally on 1st you have a significant synthetic chemical challenge ahead of you wish people have reason sole reason rose salt is that there theories for dialup polymers that predicts this fall and there are
people who want to test those theories willing to go along with a a great deal of work task OK now we will skip ahead the year 7 . 8 and I will won't talk about it for a few moments on the issue of fear is that what happens if you increase the ball comes and what turns out to have a huge increase polymer concentration is the hallmark of oil's Shrek I shall write we've already talked about dielectric relaxation day and in the dielectric relaxation data all she dielectric relaxation we increase the concentration of dielectric increments for that unit concentrations the increment molecule falls the chain's contrite however there are 2 other ways of doing the same as that of the 1st ones gathering the 2nd incident From the regional light scattering experiments using historical about your problems faced by all means memory the pollution and then lost a bet of Parliament and then looked this interesting problem suppose we do experiments on Thailand's solution it's the technique would work very well established you get following molecular weight polyethylene for example in dilute solution by looking at how much light it's clear however if you looked at a random copolymers you do get very inconsistent or reasonable results "quotation mark Oklahoma well black colorful this is what of the dialog the block of all their hollow merger that's and then the relevant files followers already have a new these but the systematic process doesn't pose a great deal of watering and so they're always like to try to measure the molecular weight of these and you don't get very sensible results in question was what they had very bright idea which they estimate Friday idea was that's the reason we're getting quite sensible results is that each chain was not the same as all of its neighbors and the water in the 80's and and therefore GOP excess scattering because there was this disk difference between 1 chain in the next March .period details of how they're so they how often we test or if the excess areas arising because the trains are heterogenous that is they don't all have the same well it's a little hard to control synthesis so what will do is to make a polymer that is asked of us dialog that is as heterogenous as possible then we will look at a mixture of these and the you can't get much and you can't get any more dramatically different composition chain by chain that this is what you see here and what they confirmed was that yes the fact that these are the same contributes to the white scaring and this proceeded along the development proceeds along point where you have these chains next match the same index of refraction as the sold people realize you can't see these anymore and you just see the behavior of the Bj and therefore if you have a large be changed or you can use scaring measure radius and stake in start substituting in a chains for sold the HA gains will cause the the changed contract exactly the behavior we talked about for dielectric relaxation but now we're using scattering seeds contraction and there were a series of experiments memories servers who are that us from the world and the observation is that if we have a chain of some size and will increase the concentration of invisible matrix chains are whereas square radius is what this government chains shrink that experiment is hard to push out high-performance comes these losses however there is a 3rd way it needs a 3rd way firm is known from scaring you can get 1 more scientifically impressive that experiment where you need a large nuclear reactor in your lineup up in order to carry things are now actually do not have a lot of reactor in your lineup instead you go away national facility there a very small in world which has a bigger reactor which produces a very large very stable very well characterized neutron flux it has little holes in the side the neutron beams filtered and and you can now use them for scattering and you were very careful to do a bunch of of things for safety of Internet result is used in scattered neutrons my might ask Why do you want to scare from the ends the 1st answer is :colon neutrons will both said through things rather plainly at least a 3rd low atomic weight and you might get absorption eventually I mean if you put if you walk around with a silver coins in your pocket and you were careless with where the neutrons are going after a while you notice the neutrons are becoming radioactive solvers becoming radioactive reactor because it's absorbing neutrons there's some interesting pre-World War cyclotron descriptions of people should be more careful and eventually work however having said that the virtue neutron scattering as they like they scared very effectively from hydrogen and from interior but they do not scare the same way again there is a large theoretical development which I am skating over but the net result is that it may take on produced during this period during happily and I put it on c of heightened hydrogenated polyethylene I mostly see only 1 of them or vise versa I really only seek 1 of and if I very glad instead I take the material that is some of they have some of texts and if I get
racial just right the neutron scattering almost does not see this and I can now produce invisible Paul chain new neutron scattering invisible Paul and I don't worry about the changes that are going to scatter and so I have mainly I have for example trace quantities of visible and large amounts of the invisible change and I can use neutron scattering on polymer that is very well characterized the material you're looking at is polystyrene toluene and all also polystyrene in carbon die sulfide Mike urbanites sulfide and contain any hydrogen it's neutron invisible was not quite neutron visible but it's good and we can plot in Figure 7 . 8 the chain radius persons policy of but and while is the view of the new part is that hasn't changed chain ratings changed the commenters concentrations the chain's now that figure is below a little more complicated than you might think if you do look at her 1st of all the 2 polymer chains are all very nearly the same size the 2 chains were looking at downloaded all the solid points are looking at 110 kilovolt polystyrene thing at all are looking at 111 kill adult polystyrene different someone I did generate this figure and this is 1 of the these things that is worth talking about how we generate figure is if you work hard you will notice there is that like a size scale on the left and right axis and they are not the same the reason is that these polymer and these 2 top solvents has a different notes that almost the same molecular weights different by 1 per cent and you should realize that saying the polymers different molecular weight by 1 per cent need you have an on reasonable confidence in your experimental that accuracy we're working with DNA where you know the molecular weights at all so what I did was say OK we'll take 2 vertical scales 1 for each set of experiments and they will have the the same top and so at 0 concentration we have the same starting point and the 2 Accies cool then cover the same fractional changes Ray that's what we do and knows the Accies quite different but all they do have the same starting point and they do both cover approximately a factor of 2 changing rates Japan's there the other problem I have images of a little more also significant is that 1 of the research firms perfectly reasonably reported the Paula concentration even of GM Perlita grams of salt per liter solution that's a very reasonable concentration you the other group reported the mole fraction and you then have little difficulty but those 2 are of wall fraction of all accepted the 2 endpoints those 2 scales are quite the same fundamentally Lyon the same the reasons we're are not the the same as something called volume of mixing the traditional freshman chemistry this kind of thing the leader of the water the Navy is not on the nature of of all aspects of people but any missiles and you know how for all practical purposes vodka however you end up with 2 leaders no you end up with does anyone have to remember the number I guess it's about that I was going to save 1 . 9 with you write you went out with but have a leader and a leader in Mexico together and as you may slip together system and France the details of their quite constant complicated the reason this is important is that if you want to confirm how many malls of this and walls of that we have or weight fraction we have so much weight that may actually be weight fraction I'm convinced members on we have 50 per cent by weight polystyrene that doesn't mean you have all given densities of . 9 roughly that doesn't mean you have 450 grams of polystyrene named leader of solutions it means you have 450 grams polystyrene in 900 grams of solutions and you cannot convert unless you do something silly during measurements ,comma released which ended up and so there to excessive concentration units bottom and how top they are arranged so infinite died Lucian and melts old polymer lineup because in the melt 100 per cent by weight and whatever it's around of 943 if I recall Grandpa leader the melts numbers are the same and so we have composed this gray after show 2 sets of data now but what is the issue here almost 2 sets of data they're both very hard to measure there were down by 2 slightly different methods all data will be used a tracer amount of polystyrene here label polystyrene King used concentrated polystyrene and used a statistical mechanics straight to pull out the radius of the labels polystyrene from the online polling centers were very controversial for a very long time because they do not agree with each other are the coronation why we interested in the spring of wealth there is any scaling theory of polymers used in that does paint a reference to the there and what is claimed to 1 where birds is concentrated along the concentration claimed that nothing happens says and that there's some sort of over which means it hasn't regions or something of that sort of happening simultaneously in theory doesn't make clear prediction and I'm out here the theoretical predictions of our squares is proportional to to seal minus for James contracted as you increase concentration and the prediction was that you get a power loss what and so there was an effort made to measure experimentally we have lost their these 2 sets of data and if you plot to data on
Wall wallpaper on you get to somewhat different expert and the black agree more with the expo was predicted and he opened up let's get a different number and since some people were very attached to the theory that there was a great deal of back-and-forth as to what was going on however point out a couple of features of this graph on emphasized quite as much except by people who aren't quite as well this year and the 1st is that if you look at that graft all in all it was crossover over and cross over her as promptly at concentrations C-Star be overlap concentration of which Parliament changed facsimile speaking our shoulder to shoulder but hadn't started in 10 straight well that's theory says that if you look at the data does this and very something like all of the 3rd of the contraction has occurred In this region where there's not supposed to be anything and contractions continues you can see the contractions and if you ask what happens ,comma in solution well contraction continues and continues all in all I'm here to do something like 500 thinks the sort of thing after all over and beyond that the search for gas continues there that's solid blocks or perhaps it runs out of steam the open that sort of shows about Paula doesn't attract much about 50 per cent by weight and the people will be happy to explain why you should be seeing them but the net result is on the curve does not look a great deal like the theory quality if you only look at the the high concentration thoughts that constantly if you only look at the dots that all but balls say 100 grams per liter you can put them on a power a lot block radius weird versus concentration you can't win the title but the variation this way isn't exactly very big variations this way is isn't exactly a huge so there's some uncertainty in the power all Members Only a great deal of dispute as to what was happening I put wanted something different from power Ipanema struggles to her solid versus stretched exponential again and you see the solid pursuit quite nicely going through all the points including low concentrations .period Powell warned us and the only difficulty occurs if you go out to the belt concentration and then that's for change sides we will not push that I will lose sight of the thought about relaxation of bone the 1st point is experimentally the easy way to do the experiment is to take the sample were between metal plates and apply an oscillating electric field that oscillates having given frequency so we have tested 25 and hostility electric field with some frequency Everything that manager but Of capacity not how you measure the capacity as well if you want do it accurately repair work the importance issue usually and this is actually physicist the comparisons of with capacitor is determined by the dielectric constant of the material between the plates look dielectric constant and if we're talking freshman we tell there is a material it has a dielectric constant in the small In the real world epsilon hands on goal dielectric constant depends on frequency you actually seen this in practice it is ask what is the dielectric constant water in it's very large if you've got off to optical frequency index of refraction is directly related to the dielectric constant yes water hasn't dielectric constant which has not won an index of refraction which is not once but it's not very big and in fact if you fall the dielectric constant 1st frequency you discover lot of America because we wanted cover lots of frequencies and we using a lot of the dielectric constant rolls off the rolls off quite dramatically will discuss details of the roll-off next time now I have what I want to 1st it's simply get to the question why isn't roll off widens the dielectric constant drop very high frequency always go back and think is voluntary and it has to be charge against this simple face waters it's a amino acid victims that charges on we apply an electric field we get a dielectric constant because the molecule and why not feel however if I have fun fled the field around some of oscillating field from all over the world has turned around through 180 degrees to manage OK that takes a lot if we are in very low frequency the molecule has no difficulty flipping and flopping each time we change the sign of the electric field in the past however Frank Frank frequency molecules starts to fly-half it can't and forced her rotated significantly the fields pointing back the way it was originally and as a result at very high street the molecules that we are not capable of keeping up with the field and they do not and they simply sit there the better but all at the festival now there's something else that can happen but does not want to dielectric constant studies that comes up and certain related studies namely all as you think change in the field around the flip and flop back and forth all you may get out of phase With the Sharjah applying here even described his ideas on applying a voltage across the plates for you it's a high flying charges on the plates you can use several different things and there is some complication is that we will not get into dielectric response so there is something I have over some outside of the
titles to relax that would happened very high frequency died holes just sit there and they do not contribute to the dielectric relaxation however the dipole still the molecule still have electrons and the electrons shuttled back and forth in molecules do not have time road and sell at very high frequencies way way out after most still have dielectric response would be too much smaller because it just correspond to the electrons on however the molecular rotation or local rotation part of the dipole behavior doesn't contribute
Magnetisches Dipolmoment
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Berg <Bergbau>
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Initiator <Steuerungstechnik>
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Metadaten

Formale Metadaten

Titel 9 Dielectric Relaxation, Part 2
Serientitel Classes in Polymer Dynamics
Teil 9
Anzahl der Teile 30 (Lecture 2 missing)
Autor Phillies, George
Lizenz CC-Namensnennung 3.0 Unported:
Sie dürfen das Werk bzw. den Inhalt zu jedem legalen Zweck nutzen, verändern und in unveränderter oder veränderter Form vervielfältigen, verbreiten und öffentlich zugänglich machen, sofern Sie den Namen des Autors/Rechteinhabers in der von ihm festgelegten Weise nennen.
DOI 10.5446/16235
Herausgeber Phillies, George
Erscheinungsjahr 2012
Sprache Englisch

Inhaltliche Metadaten

Fachgebiet Physik
Abstract Lecture 9 - dielectric relaxation, part 2. George Phillies lectures on polymer dynamics, based on his book "Phenomenology of Polymer Solution Dynamics".

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