Questions tagged [polymers]

Polymers is concerned with the physical properties of individual macromolecules. For questions regarding bulk behavior of ensembles of polymers, the [condensed-matter] tag may be more appropriate.

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Derivation of probability density of isolated polymers

I am reading Introduction to Polymer Physics by Doi, and in his proof for the probability distribution for ideal polymers of length $N$ and end-to-end vector $\mathbf{R}$, he does the following: \...
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39 views

Canonical partition function, simple model of 2D polymer

I am trying to simulate using monte-carlo method the behavior of a simple of polymer. The model - The polymer is made of N bars with length a , each bar can be placed in +a or -a relative to the end ...
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23 views

Average radius of gyration of an ideal chain anchored to a wall at two ends

Suppose you have an n-monomer ideal chain with both ends constrained to be at the same point on an infinte wall (as shown below). Using the method of images, the partition function can be shown to be ...
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39 views

Discriminate closed-chain from open-chain

I have two classes of chains: closed-chains where a random path ends near where it starts (ie. loop), and open-chains without this restriction (ie. random walk). These chains are a directed graph ...
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29 views

Having trouble understand why excluded volume effect occurs

In the book of Edwards The Theory of Polymer Dynamics, at page 24 it is given that 2.5 Excluded volume effect In the models of polymers considered in the previous sections, the interaction among the ...
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38 views

Worm-like chain model integral formula derivation (Kratky-Porod model)

I am having trouble understanding the derivation of the integral formula, most papers just assume the resistance to bending is: $$\frac{A}{2}\left|\frac{dt(s)}{ds}\right|^2.$$ I have found some ...
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57 views

Why does burning polythene bags cause shrinkage while cutting them makes no change?

I don't know why polythen bags shrink on burning. But one of my friend informed me that it shrinks because at the time of its processing, the polymer is stretched and when burnt the internal stress ...
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1answer
24 views

Converting order parameter to director (nematics)

If I have a differential equation for the order parameter of a uniaxial nematic, like $\frac{\partial S_{\alpha \beta}}{\partial t} = f(S_{\alpha \beta})$, for $S_{\alpha \beta} = S(n_{\alpha}n_{\beta}...
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Are the breakdown voltages of silicon dioxide and silicone dioxide the same?

Silicon dioxide has a breakdown voltage of $> 10$ MV/cm [1]. However, I am unable to find any information about the breakdown voltage of silicone dioxide. Since silicone contains oxygen (and ...
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36 views

Using Persistence length to establish straightness of position data

In the following picture I am showing 3D position data for 4 different tracks just to illustrate how the tracks looks like. As we can see that we have all kind of behaviors occurring from helical ...
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Does sputtering Au on top of PEDOT:PSS thin film alter its properties?

I have grown thin films (~100-500 nm) of PEDOT:PSS by electrodeposition on top of thin films of Au (~1 nm) and now I want to measure the impedance of the PEDOT:PSS thin film. To accomplish this I am ...
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37 views

How does contraction of polyethylene strip depend upon the heat it receives?

Strip is made of polyethylene and is cold drawn so that all polymer chains are oriented in one direction. Now, if heat is supplied to it via external source then how much will this strip contract. Is ...
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53 views

Exploring potential landscape with Monte Carlo

I am using a Monte Carlo approach for studying folding of a polymer chain. The polymer may fold in many configurations, corresponding to local potential minima, studying which is what interests me (i....
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526 views

Temperature dependence of rubber elastic modulus

Why does the elastic modulus of rubber increase with temperature? I read the article on rubber elasticity and it showed that the modulus increases with the temperature (rubber shrinks as heated). But ...
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38 views

Entropy due to linearization of Freely-Jointed Chain

Say I model a polymer as a freely jointed chain in 3D with N bonds of length L each one. If I stretch the chain (initially coiled) along a 2D surface until it becomes linear (basically a 1D line of ...
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1answer
28 views

Can the UV degradation of polymers be calculated?

Is it possible to calculate the mass lost due to the UV degradation of polymers (like PET or LDPE)? I have found no information regarding equations or formulas which would provide an answer. Any ...
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37 views

Why do stress whitening occur on certain polymers?

In polymers under strain, white lines start to appear first before fracture..what are they? And why they occur?
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65 views

Text Recommendation: Random Walks (for physicists)

I am an incoming graduate student in Theoretical Physics in the Netherlands, and I would like to know if any of you could recommend texts on random walks with applications to physics. My university ...
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65 views

Solids are crystalline or amorphous. Where do polymers fit in?

Traditionally, solids are classified as being either crystalline (well-ordered, periodic lattice structure at large spatial scales) or amorphous (disordered structure). A well-ordered polymer is a ...
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205 views

What is the link between the meaning of excluded volume and its mathematical derivation?

When we examine real polymer chains we have to consider the interactions between single monomers. Therefore we consider a Lennard-Jones-like potential for bringing two monomers together and calculate ...
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784 views

One-dimensional polymer (Gibbs canonical ensemble)

Let's consider a polymer that is formed by an horizontal linear chain of $N$ disc-shaped monomers. Each monomer can either adopt either a vertical alignment (with length $l_1$ and energy $E_1$) or an ...
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46 views

Can any body suggest me a set up that I can build it up to study the surface roughness of transparent polymeric fibres? [closed]

I need to study the surface of nylon-6 blank fibres with a thickness of nearly 40 micrometre. I work in optics lab with many optical components such as beam splitters, lenses, mirrors, etc; can I ...
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28 views

Can I build up a profilometry set up, to study the surface roughness of polymer fibres?

I need to study the surface roughness of some fibres, I was told that the best way is the profilometer, but can I design and build up a set up of a profilometer?
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What does triviality and non-triviality mean in field theory?

I am studying polymer physics and their basic field theoretical models which has connections to $\Phi ^{4}$ field theory. I frequently come in touch with statements about triviality and non-triviality ...
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Is there any connection between instantons and surface-interacting polymers?

Excluded volume polymers interacting with a penetrable hypersurface of variable dimension is a very interesting system to study critical behavior via perturbative renormalization. Since a penetrable ...
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2answers
670 views

Reason for very low speed of sound in rubber

I just came by a table in the Class 11 Physics NCERT textbook, listing speeds of sound in different media. Vulcanised rubber has an unusually low speed of sound $54\ \mathrm{m}/\mathrm{s}$ as compared ...
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135 views

Reference Request - Modern Polymer Dynamics

I'm an applied math graduate student studying the cytoskeleton. I wanted to know of any reference(s) providing the most general mathematical theory of polymer dynamics, think an updated version of Doi ...
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452 views

Derivation of the upper convected time derivative

I read on wikipedia theat the upper convected time derivatvie is the rate of change of some tensor property of a small parcelof fluid that is written in the coordinate system rotating and stretching ...
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47 views

How to calculate path integral of polymer system?

We have the functional integral $(1)$ of viriable $\delta p_j$. In our case this intergral follows from RPA (random phase approximation) method assuming $\ p_j(r)=p_j^*+\delta p_j(r)$. The task is to ...
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21 views

Does crosslinking a polymer film increase the stress within the film?

If I crosslink a polymer film, does that increase the internal stress of the film? Intuitively I think it should for entropy reasons; chains with greater links are more restricted and have a smaller ...
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3k views

How do UV light curable adhesives work?

How do UV light curable adhesives (such as Loctite's and Permabond's UV glues) work? What gives them the ability to join two non-porous surfaces such as glass-to-glass, glass-to-metal? Also, do ...
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42 views

How to theoretically determine thermal emissivity of thin polymeric films?

Maybe someone could help with determining gray-body emissivity of thin films such as polyethylene. There is a lot of conflicting data online with some sources stating polyethylene's epsilon value as 0....
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1answer
104 views

Linking elastic moduli to shape fluctuations

I am simulating a polymer network shaped as a sphere. I would like to compute its elastic moduli (bulk and Young's, for example) not by their shear-strain definition but by looking at the fluctuations ...
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1answer
1k views

Why do rubber bands at higher temperatures stretch more?

I did an experiment where i placed a rubber band in water at different temperatures (-15°C till 90 °C) , and then a put a constant mass on the rubber band, to see how far it would stretch. What i ...
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553 views

Elasticity of rubber bands at varying temperatures

So what i read online was that when rubber bands can stretch (become more elastic) more when their at colder temperatures. How i understood is that entropy allows for the molecules to align up more ...
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69 views

Unexpected behaviour in numerical simulation of polymer

I noticed some strange behaviour when simulating the behaviour of a polymer subjected to an external pulling force at both ends, and would like to better understand its origin. I used LAMMPS to ...
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1answer
513 views

Understanding roles of energy and entropy in different polymer models

Polymers can be modeled as ideal chains and bead-springs (among other various models). However, in an ideal chain, the interactions are entirely entropic, whereas in the bead-spring model, there are ...
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1answer
4k views

Relationship between Kuhn length and persistence length

What is the persistence length of poly(N-isopropyl acrylamide)? Is there a definite relation between kuhn length and persistence length? I know that the persistence length is considered to be one ...
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1answer
759 views

Why melting temperature of polymers depends on the prior crystallization temperature?

This graph should show that the melting temperature of a polymer rises when the crystallization temperature of a polymer was higher (the melting temperature of a 100% crystalline polymer should be ...
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1answer
123 views

Simple model of a polymer

Let's describe a polymer as a linear chain of $N$ links which all have a bendable part. The energies of one link are $\epsilon_-$ (unbended) and $\epsilon_\wedge$ (bended). Additionally, the lengthsof ...
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111 views

Can anyone explain this condensation pattern?

What is the hair-like "polymer" that condenses on the caps of the plastic cell vial? Inside vial are cells in a mixture of FBS and DMSO. The vials were frozen slowly in a special isopropanol-filled ...
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1answer
38 views

How can the presence of a solvent be included in a polymer bead-spring model?

I have a bead-spring model of a polymer melt and I would like to simulate what happens when a solvent is added to the system. The most direct way to do this would be to add solvent particles into the ...
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101 views

Pressurizing with nitrogen vs vacuum? [closed]

pressurizing with vacuum causes volatilization of liquid.
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517 views

Molecular Dynamics Software for Coarse Grained Polymers

I am looking around for MD software that I can use to simulating polymers and I can't decide which software I should use. I would like to simulate the swelling of crosslinked polymers, and I would ...
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1answer
196 views

Standard linear solid model - dashpot "short out" at $t=0$

My professor said that at $t=0$ the dashpot in standard linear solid is "short out". Why? I know that the force of dashpot is ($u$ is the dislplacement): $$F_{\eta}=\eta \space \frac{du}{dt}.$$
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249 views

Stress relaxation time scale [closed]

What is the definition and physical meaning of "stress relaxation time scale" in (non-Newtonian) fluids?
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22 views

Electret analog of Curie temperature

If you heat a permanent magnet above its Curie temperature then individual dipoles re-align to cancel each other out and it loses its strength. An electret is the electrical analog of a permanent ...
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3k views

What do people mean with "per unit volume" in polymer solutions theory?

I am reading Modern Theory of Polymer Solutions by Hiromi Yamakawa and in the context of the virial expansion the following puzzles me a bit: "...expanded in terms of solute concentration $c$ (in ...
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1answer
79 views

Scaling argument for friction force on a chain in shear flow

In her paper entitled "Deformations of One Tethered Chain in Strong Flows", the author makes the argument that given a shear flow velocity $v_x(y)=sy$ in a solution of viscosity $\eta$, and a tethered ...
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2k views

partition function for polymer chain

Supposing that I have linear chain with polymer of $N$ identical particles (interacting harmonically with adjacent particle) with position of first and last particle fixed, how do I find the partition ...