Semicrystalline polymers block copolymers

Creton, C., Kramer, E.J., Hui, C.-Y. and Brown, H.R., Failure mechanisms of polymer interfaces reinforced with block copolymers. Macromolecules, 25, 3075-3088 (1992). Boucher et al., E., Effects of the formation of copolymer on the interfacial adhesion between semicrystalline polymers. Macromolecules, 29, 774-782 (1996). 

Formation of physical cross-links by the anchorage of chain ends in semicrystalline domains and production of permanent entanglements is shown in the HBIB block copolymers. No such arrangement exists for the inverted polymer HIBI. (No attempt has been made to show possible chain folding, or superstructure development of their... 

Binary composite membranes constitute the chief example of membranes classified under (b) in the introductory section. They include binary polymer blends or block or graft copolymers exhibiting a distinct domain structure, filled or semicrystalline polymers and the like. 

As a route for improving the melt-elongational properties of semicrystalline polymers, Siripurapu et al. [7] proposed the blending of amorphous and semicrystalline blends of PS and PVDF nevertheless, their approach showed only limited success. In contrast, Reichelt et al. [29] successfully developed blends of HMS-PP and PP-fe-PE block copolymers. As could be shown, the melt strength increases with the HMS-PP content, while blends rich in HMS-PP also show the lowest densities. 

Table 4.3 shows the permselectivity characteristics of pure, semicrystalline PEO films [76]. The selectivity characteristics for 02/N2 are rather similar to those for silicone rubber and natural rubber shown in Table 4.2. However, the values of permselectivity for C02 relative to the various light gases shown are all much higher than Table 4.2 shows for the rubbery polymers listed there and even for polysulfone except for C02/CH4. Comparison of the data in Tables 4.2 and 4.3 makes it clear that this high permselectivity of PEO stems from its high solubility selectivity for C02 versus other gases this is augmented by modest values of diffusivity selectivity. Data in Table 4.4 for the C02/N2 pair illustrate that this effect can be translated into various block-copolymer structures when the PEO content is high enough to ensure it is the continuous phase. In fact, nearly all these materials have higher permselectivity and solubility selectivity for C02/N2 than does pure PEO (see Table 4.3) however, the diffusion selectivity for these copolymers is much closer to, or even less than, unity than seen for pure PEO. Furthermore, the copolymers all have much higher absolute permeability coefficients than does PEO.

A number of theories of the contribution of interdomain polymeric material to the stress-strain, modulus, and swelling behavior of block copolymers and semicrystalline polymers are examined. The conceptual foundation and the mathematical details of each theory are summarized. A critique is then made of each theory in terms of the validity of the theoretical model, the mathematical development of the theory, and the ability of the theory to explain experimental findings. 

A number of polymeric systems exhibit domain formation. This results in some polymeric material being confined in regions between the domains. The deformation properties of these systems depend on the types of polymer chains lying between the domains, as well as on the shape and spatial arrangement of the domains. Several theories have been proposed to date for the contribution of the interdomain material to different deformation properties in semicrystalline polymers and block copolymers. We will present and analyze these theories herein. 

Another remarkable character of this class of Ni complexes is their tendency to promote living polymerization of a-oleftns at low temperatmes and with low concentrations of the monomer. Thus, the low-temperatme polymerization of propylene leads to a material whose number average molecular weight (Mn) increases almost linearly as a function of time and propylene consumption, reaching values ofM = 160 000 Daltons and polydispersities of ca. 1.13. This character allows these Ni catalysts to produce A-B-A type block copolymers composed of semicrystalline and amorphous segments, which is used to prepare thermoplastic elastomeric polymers. The Ni catalysts can also polymerize internal cyclic... 

Practical problems associated with infrared dichroism measurements include the requirement of a band absorbance lower than 0.7 in the general case, in order to use the Beer-Lambert law in addition infrared bands should be sufficently well assigned and free of overlap with other bands. The specificity of infrared absorption bands to particular chemical functional groups makes infrared dichroism especially attractive for a detailed study of submolecular orientations of materials such as polymers. For instance, information on the orientation of both crystalline and amorphous phases in semicrystalline polymers may be obtained if absorption bands specific of each phase can be found. Polarized infrared spectroscopy can also yield detailed information on the orientational behavior of each component of a pol3mier blend or of the different chemical sequences of a copoljnner. Infrar dichroism studies do not require any chain labelling but owing to the mass dependence of the vibrational frequency, pronounced shifts result upon isotopic substitution. It is therefore possible to study binary mixtures of deuterated and normal polymers as well as isotopically-labelled block copolymers and thus obtain information simultaneously on the two t3q>es of units. 

This review has illustrated various properties of multiphase polymer systems obtained from computer simulation. Three modeling techniques - atomistic, coarse-grained, and atomistic-continuum modeling - are applied to miscibility of homopolymer/copolymer and homopolymer/homopolymer blends, compat-ibilizing effect of block copolymers, and mechanical properties of semicrystalline polymers, respectively. 

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