Copolymer miscibility

It has been found by Baird and others [74-77] that the presence of LCP may accelerate and presumably direct the crystallization of conventional polymers (PET, etc.). Porter [76] has shown that, by blending biphasic polymers such as the PET-poly HBA copolymers, miscibility may be achieved between the conventional phase of the biphasic polymer with another conventional polymer that component is miscible with, i.e., X7-G/PBT. The latter phenomena may offer direction in the search for useful compatibilizing agents for LCP/conven-tional polymer systems. 

The present review is mainly concerned with the preparation and functionalization of micro compositional materials with cellulosic polysaccharides as the principal component, including four major categories graft copolymers, miscible or compatible polymer blends and networks, polysaccharide/inorganic nanohybrids, and mesomorphic ordered systems. Ultrathin layers of cellulosic... 

Since PEC is a copolymer, description of its interaction with PS is more complex than if it were simply a homopolymer. Binary interaction models have been presented which suggest that copolymer miscibility with a homopolymer can be enhanced by endothermic interactions between the unlike repeat units of the copolymer (11-13). In its simplest form (11). the binary interaction model for the heat of mixing, AHaix, of a copolymer. A, containing repeat units 1 and 2, with a homopolymer, B, containing repeat units 3, is given by... 

Styrene copolymer/ Miscibility detected by Miscibility strongly depends on Chen and Morawetz,... 

This concept is, in essence, the result of neighboring units of a copolymer having a lower affinity for these units than the units of another polymer or copolymer. Miscibility can occur if the interaction energy (interaction parameter) is more positive for the copolymer units than the interactions between these units and the admixed polymer. Cases can easily exist where all the... 

COPO blends with styrene/vinyl phenol copolymers - miscible... 

Krause [25] and Helfand [26] have given theories, based on lattice models, for estimating block copolymer miscibilities including the type of interface developed between the microphases in these systems. Coleman, et al. [27] have assessed the validity of solubility parameters in estimating the miscibility of polymer pairs. 

J. Dudowicz, K.F. Freed, Energetically driven asynunetries in random copolymer miscibilities and their pressure dependence. Macromolecules 30(18), 5506-5519 (1997)... 

Polymer pairs containing one monomer in common (at least one of these must be a copolymer), miscible in the amorphous state at room temperature. One or both of the polymers may be semicrystaUine. 

Micellar objects and micelle-like domains are induced by low amounts of MAM (5-20 wt%) and presented a core-shell structure, with the core identified as PMMA and the shell as PBA surrounded by PMMA chains of the copolymer miscible with the PMMA matrix. Micelle density seemed to be constant in the solid unfoamed precursors with values of approximately 4-4.5 x 10 " micelles/cm. Moreover, the apparent size of the micelles varies from 20 nm in 95/5 PMMA/MAM blends to 50 nm in 80/20 PMMA/MAM blends, with the core size approximately one-third of the micelle size (Fig. 9.11). This evolution of the nanostructure was noticed as unexpected and related to the processing conditions during the self-assembly of the nanostructuration, probably out of equilibrium. In addition, it was noticed that the injection procedure induces an orientation or even an elongation of the micellar-like domains in the injection direction (Fig. 9.12). On the contrary, 25/75 PMMA/MAM blends showed no influence of the injection process on the orientation of the nanostructure, with poorly defined lamella of 20-30 nm apparent thickness. 

Intramolecular Repulsive Interactions. Miscible blends can also be achieved in absence of specific interactions, by exploiting the so-called intramolecular repulsive effect. This is observed in mixtures where at least one of the components is a statistical copolymer miscibility is restricted to a miscibility window, that is, it takes place within a well-defined range of copolymer composition. For example, poly(styrene-co-acrylonitrile) (SAN) and poly(methyl methacrylate) form miscible blends for copolymer compositions in the range 9-39% acrylonitrile (26,27). Miscibility in these systems is not a result of specific interactions but it is due to the intramolecular repulsive effect (28) between the two monomer units in the copol5uner such that, by mixing with a third component, these imfavorable contacts are minimized. The same situation is encoimtered in binary mixtures of two copol5uners (29). 

Binary interaction model Intramolecular repulsions Copolymer-homopolymer miscibility Copolymer-copolymer miscibility Terpolymer-terpolymer miscibility Terpolymer-homopolymer miscibility Mean-field approach to obtain interaction parameters Spinodal and phase separation... 

S. K. Kumar, Thermodynamics of random copolymer miscibility, PMSE, Proc. of the 214th American Chemical Society National Meeting, Dallas, TX, Vol. 78, 120, March/ April, 1998.. 

Chlorinated polyethylene offers miscibility with PVC at levels of 42 wt% Cl and higher, offering permanent plasticization potential [853]. At lower Cl levels, phase separation occurs but mechanical compatibility allows for impact modification of rigid PVC [854]. Poly(butylene terephthalate) (PBT) [855] and poly(butylene terephthalate)-poly(tetramethylene ether) (AB)n block copolymer miscibility [856-858] with PVC has been reported. NMR revealed pure phases of microcrystallites of both the block copolymer and PVC with miscibility of the amorphous phase [858]. 

The reactive compatibilization of a binary A7B immiscible polymer blend is usually ensured via the use of a chemical reaction during the melt-blending operation. The reaction leads to the formation of block or graft copolymers miscible, or at least sufficiently compatible, with both polymers A and B. Depending on its chemical composition and molecular architecture, the in situ formed copolymer is able to locate at the interface, improves the adhesion between the two phases, and constitutes a stabilizing barrier against coalescence (Fig. 22.8). 

Chapter 1 covers experimental techniques widely used in studies of polymer crystalhzation. Chapter 2, Chapter 3, Chapter 4, and Chapter 5 are devoted to the structure of crystalline polymers and also to the kinetics of nucleation and growth of the crystaUine phase. Chapter 6 is focused on molecular modeling of polymer crystallization, whereas Chapter 7 describes overah crystalhzation kinetics, with special reference to the theories widely used in practice. Chapter 8 covers the subject of epitaxy. Chapter 9 is dedicated to melting of polymer crystals. Chapter 10, Chapter 11, and Chapter 13 describe the crystahization in copolymers, miscible and immiscible polymer blends, and also polymer composites. Chapter 12 is focused on phenomena related to the confinement of polymer chains. Chapter 14 describes the effect of flow on crystahization, and finally Chapter 15 covers the crystalhzation in processing conditions. 

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