Random Chain Coils

Theta conditions are of great theoretical interest because the diameter of the polymer chain random coil in solution is thenequal to the diameter it would have in the amorphous bulk polymer at the same temperature. The solvent neither expands nor contracts the macromolecule, which is said to be in its unperturbed state. The theta solution allows the experimenter to obtain polymer molecules which are unperturbed by solvent but separated from each other far enough not to be entangled. Theta solutions are not normally used for molecular weight measurements, because they are on the verge of precipitation. The excluded volume vanishes under theta conditions, along with the second virial coelTicient. 

In the first case, the molecules vitrily, with the polymer chains randomly coiled and entangled. The resulting solid is amorphous and is hard and glassy. 

Polymer chain Random coil arrangement Degree of local order. Can be annealed to control the level of crystallinity. If too high, polymer is brittle... 

Property Rigid Rod Extended Chain Random Coils... 

There are too many other possibilities of disorder, and I think the same thing of, say polydimethylsiloxane. Again, you can have, if you took the extreme three models you could think of for PDMS, regular chains, random coils, and freely rotating chains the fteely rotating chain fits best. There have been some people who have argued for polydimethylsiloxane, who in actual fact put it in delocalized states. 

Despite the absence of theoretical expressions, the practical apphcations of oriented crystallization have been developed and commercialized. The most important appUcation is in the synthesis of high-modulus fibers from conventional, flexible-chain, random-coil polymers such as polyethylene. In the process of solid-state extension (similar to the experiments of Southern and Porter), almost perfectly oriented, extended-chain structures are obtained by forcing a polymer billet through a tapered die. A major use of such fibers is in the reinforcement of composites. 

The basic features of folding can be understood in tenns of two fundamental equilibrium temperatures that detennine tire phases of tire system [7]. At sufficiently high temperatures (JcT greater tlian all tire attractive interactions) tire shape of tire polypeptide chain can be described as a random coil and hence its behaviour is tire same as a self-avoiding walk. As tire temperature is lowered one expects a transition at7 = Tq to a compact phase. This transition is very much in tire spirit of tire collapse transition familiar in tire theory of homopolymers [10]. The number of compact... 

Step I. The time dependent structure of the interface is determined. Relevant properties may be characterized by a general function H(t), which for the ca.se of polymer melts can usually be described in terms of the static and dynamic properties of the polymer chains. For example, with symmetric (A = B) amorphous melt interfaces, H(t) describes the average molecular properties developed at the interface by the interdiffusion of random coil chains as [ 1,6J... 

How do highly interpenetrated random coil chains disentangle to cause fracture Disentanglement is considered to occur as shown in Fig. 14, where we depict the response of an entangled chain to a constant (step function) draw ratio X as follows ... 

Conventional rubbers are members of the polymer family in that they consist of long chain-like molecules. These chains are coiled and twisted in a random... 

The crossover 2d 2d behavior can be described in a similar manner to the case of a tube confinement. For the chain, trapped between two parallel plates a distance D apart, one again has N/g blobs but they arrange to a two-dimensional random coil configuration ... 

How does the polymer chain sneak out from the entangled random coil state and how does it order into a crystalline state ... 

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