Polymers in the bulk state

This means that a polymer coil with Z = 2 and a degree of polymerisation M/M of 104can be extended about 50-fold. This deformability of the isolated molecule is closely related to the reversible deformability of elastomeric polymers in the bulk state. 

Basic to this review is the intent to bring together methods and the basic principles of their application by which specific or average orientational parameters) may be obtained and interpreted and to point out some new technological and theoretical advances made that can be usefiilly applied in reaching a better understanding of molecular behavior of polymers in the bulk state. 

Equation (7.24) indicates that, if the foam is required to have a certain compressive yield stress, yet minimum density, the yield stress of the polymer in the bulk state must be high. Polystyrene has a yield stress at high strain rates of 120MPa whereas polypropylene has a yield stress of 60 MPa. Consequently, an EPS helmet will have a lower density than an EPP helmet designed to meet the same impact tests. Therefore, EPS is optimal for helmets that offer single-impact protection. 

The material studied here is a particular solid a polymer melt, i.e. a polymer in the bulk state above the glass transition temperature and crystallisation temperature Tj. 

Why is the radius of gyration of a polymer in the bulk state essentially the same as measured in a 0-solvent but not the same as in other solvents ... 

Except some recent studies [58, 59], preparation of polymers with spatially graded morphologies have so far heavily relied on polymerization of a guest monomer or on the spatial distribution of a guest polymer inside a host polymer in the bulk state generated through diffusion or sorption [60, 61]. The experimental data... 

Confinement within AAO nanopores produces lower degrees of crystallinity than those obtained for neat polymers in the bulk state [190,191,202]. Similar results have been obtained for the confined crystallization of micro- and nanodomains within block copolymers and polymer blends (see [92,97] and references therein). 

PHYSICAL PROPERTIES AND FRICTION COEFFICIENTS FOR SOME COMMON POLYMERS IN THE BULK STATE... 

Two of the most important functions in the application of neutron scattering are the use of deuterium labelling for the study of molecular confomiation in the bulk state and the use of deuterium solvent in polymer solutions. In the following, we will consider several different applications of die general fomuda to deuteration. 

The term polymer is derived from the Greek words poly and meros, meaning many parts. We noted in the last section that the existence of these parts was acknowledged before the nature of the interaction which held them together was known. Today we realize that ordinary covalent bonds are the intramolecular forces which keep the polymer molecule intact. In addition, the usual type of intermolecular forces—hydrogen bonds, dipole-dipole interactions, and London forces—hold assemblies of these molecules together in the bulk state. The only thing that is remarkable about these molecules is their size, but that feature is remarkable indeed. 

In this chapter we examine the flow behavior of bulk polymers in the liquid state. Such substances are characterized by very high viscosities, a property which is directly traceable to the chain structure of the molecules. All substances are viscous, even low molecular weight gases. The enhancement of this property due to the molecular structure of polymers is one of the most striking features of these materials. 

The conformation of polymer chains in an ultra-thin film has been an attractive subject in the field of polymer physics. The chain conformation has been extensively discussed theoretically and experimentally [6-11] however, the experimental technique to study an ultra-thin film is limited because it is difficult to obtain a signal from a specimen due to the low sample volume. The conformation of polymer chains in an ultra-thin film has been examined by small angle neutron scattering (SANS), and contradictory results have been reported. With decreasing film thickness, the radius of gyration, Rg, parallel to the film plane increases when the thickness is less than the unperturbed chain dimension in the bulk state [12-14]. On the other hand, Jones et al. reported that a polystyrene chain in an ultra-thin film takes a Gaussian conformation with a similar in-plane Rg to that in the bulk state [15, 16]. 

The use of ionizing radiation to induce cross-linking is another important technique for producing hydrogels from linear water-soluble polymers. When such polymers are bombarded by ionizing radiation, either in the bulk state or in solu-... 

JThe effect of the substituent on the properties of the polyphosphazenes is not fully understood. For instance, [NP(OCH ) ]n and [NP C CH. homopolymers are elastomers (8,29). Synthesis using lithium, in contrast to sodium, salts is claimed to produce rubber-like fluoroalkoxyphosphazene polymers (30). The presence of unreacted chlorine or low molecular weight oligomers can affect the bulk properties (31,32). Studies with phosphazene copolymers both in solution and in the bulk state (29,33-38) indicate a rather complex structure, which points out the need for additional work on the chain structure and morphology of these polymers. 

The self-assembly of block polymers, in the bulk, thin film and solution states, produces uniformly sized nanostructured patterns that are very useful for nanofabrication. Optimal utilization of these nanoscopic patterns requires complete spatial and orientational control of the microdomains. However, the microdomains in the bulk state normally have grain sizes in the submicron range and have random orientations. In block copolymer thin films, the natural domain orientations are generally not desirable for nanofabrication. In particular, for composition-asymmetric cylindrical thin films, experimental... 

Figure 14.7 Dependence of the zero-shear viscosity, uo, on molecular weight, M, for different dendrimer systems. (1) Dendrimers of different chemical composition but in the same state (i.e. PAMAM, PPI and PBzE dendrimers in bulk D, C and E, respectively). (2) Compositionally identical dendrimers (i.e. PAMAMs) in solutions and in the bulk state (A, B and D, respectively). (3) Compositionally identical dendrimers and linear polymers of comparable molecular weights (i.e. PAMAMs in the bulk state D and F, respectively)...

Although the above work was serendipitous, the study of concentration fluctuations in bulk polymers should be a fruitful area of research. Intentional polymer mixtures could be prepared which would allow the mutual diffusion of polymers in polymers to be obtained. Although the molecular weights might need to be kept low, the measurement of polymer motions in the bulk state would be very valuable. 

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