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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What is the persistence length of a polymer?

In Wikepedia these are the definitions for the persistence length: Informally, for pieces of the polymer that are shorter than the persistence length, the molecule behaves rather like a flexible ...
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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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38 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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Inside a shell full of strings, what are the components of the network, and what the possible defects?

Imagine that we have a (very) large shell full of holes, and flexible strings go (randomly) from one hole to another. Inside the shell, there will be a network of strings. Can one split this network ...
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74 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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39 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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18 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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How interferometric techniques can be used to investigate the topology of polymers?

I need to study the topography of a specific polymer, knowing that my lab is an optics lab with many interferometric techniques, how can I use these techniques to investigate the topology?
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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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38 views

Van der Waals interaction

i know how to calculate the Van der Waals interaction for two small volumes using the below equation, $$I = \frac{\delta V_1 \cdot \delta V_2 \cdot H}{r^6 \cdot \pi^2}$$ where H is the Hamaker ...
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Statistical model for local polymer concentration

I'm trying to describe the local constraining of two points located on a 2-part DNA polymer (double and single stranded), with respect to one fixed end. See the schematic below: Here I would like to ...
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1answer
73 views

Interesting speed of sound observation

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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58 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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48 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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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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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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222 views

Normal modes and normal coordinates of polymer chain

Is it possible to solve to get the normal modes and normal coordinates of polymer chain (which is in 3D space) with nearest neighbour interaction (harmonic interaction). Kindly suggest some reference ....
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578 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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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
58 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
530 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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268 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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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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214 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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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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316 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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68 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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81 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
37 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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92 views

Pressurizing with nitrogen vs vacuum? [closed]

pressurizing with vacuum causes volatilization of liquid.
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441 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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161 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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154 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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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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1k 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
64 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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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 ...
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Is a folded protein's conformation subject to thermal fluctuations?

In biology class we learn that proteins are folded, and that the shape the protein takes affects its bioactivity. Typically we don't go much further into protein shape from that, at least not at the ...
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761 views

Hindered rotation model for flexible polymers: deriving the Flory characteristic ratio

In the hindered rotation model we assumes constant bond angles $\theta$ and lengths $\ell$, with torsion angles between adjacent monomers being hindered by a potential $U(\phi_i)$. In Rubinstein's ...
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2k views

Difference in viscosity-concentration and reduced viscosity-concentration graphs

I prepared 3 different polymer solutions with varying concentration of 100, 50 and 25 ppm in order to measure their viscosity . When I plot concentration vs viscosity graph in the excel, I have a ...
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Why polymeric solids are said to be intermediate between crystalline solids and amorphous solids?

Crystalline solids have ordered arrangement and amorphous solids do not. Polymeric solids are simply formed by the joining of some monomeric units. It has nothing to do with ordered or not ordered ...
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57 views

Effective length factor of a polymer in solution

If one wants to calculate the force needed to buckle a polymer in solution with Euler buckling, what would the effective length factor be? The polymer is free to move and rotate in solution as it sees ...
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1k views

Calculating relaxation time

When exploring the viscoelastic properties of glassy polymer like PMMA, there are usually two relaxation mechanism: alpha and beta. Usually beta relaxation time varies with temperature following ...
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Probability of sequence for given rate constants

Consider a copolymer, $C_{r,s}^A$ containing $r$ number of $A$ monomers and $s$ number of $B$ monomers with $A$ at the reactive end of the polymer. The equilibrium constant for $A$-$A$, $A$-$B$, $B$-$...
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2k views

Where I can find information about how helium gas diffuses through different polymer materials

I need more experimental information about helium gas diffusion in solid materials such as different plastics, metals, ceramics etc. For example I am scientifically curious about what is the polymer ...
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1answer
2k views

Flory-Huggins ternary phase diagram with a neutral component

I am searching the literature for the Flory-Huggins phase diagram with the following components : polymer, solvent, and a third component that does not interact with the other components (just entropy ...
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329 views

Thermodynamics, chaperones: How to model polymer fragmentation?

Living polymers are well described by equilibrium statistical physics. Now I would like to consider a case were living polymers undergo fragmentation due to chaperones. I can think of a kinetic ...
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244 views

liquid polymers of high molecular weight

We often see a limit of melting point as a function of polymer chain length. Polyethlyene tops at about 190C, and polyethlyene glycol saturates at only 67C no matter how long the chain is: http://www....
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247 views

Deriving equations of motion of polymer chain with Hamilton's equations

This is related to a question about a simple model of a polymer chain that I have asked yesterday. I have a Hamiltonian that is given as: $H = \sum\limits_{i=1}^N \frac{p_{\alpha_i}^2}{2m} + \frac{1}{...