By M. Matsuo, S. Sagaye (auth.), Gunther E. Molau (eds.)
The molecules of block and graft copolymers are molecules of a better order; they encompass homopolymer subchains that are interconnected through chemical valence bonds. This structural com plexity is manifested within the strange habit of block and graft copolymers either in resolution and in bulk. many sorts of interac tions are attainable in block and graft copolymers within the sturdy nation. Polymer subchains of 1 molecule can engage with different polymer subchains that can belong to an analogous molecule or to diverse molecules. considering polymer chains of chemically various composition are typically incompatible, thermodynamically damaging in addition to thermodynamically favorable interactions exist within the reliable kingdom. In suggestions of block and graft copolymers, the sit down uation turns into much more advanced, simply because interactions among the solvent molecules and many of the subchains of the copolymer mole cules ensue as well as the interactions among the polymer chains. This multitude of interactions provides upward push to a large spec trum of colloidal and morphological homes that have no paral lel in much less advanced polymer structures corresponding to homopolymers or random copolymers. examine at the colloidal and morphological habit of block and graft copolymers is a comparatively new box of activity. It began in 1954, whilst F. M. Merrett fractionated combinations of grafted na tural rubber with the corresponding homopolymers and saw that colloidal sols have been shaped at sure issues in the course of his fractional precipitations.
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Extra info for Colloidal and Morphological Behavior of Block and Graft Copolymers: Proceedings of an American Chemical Society Symposium held at Chicago, Illinois, September 13–18, 1970
At 20 oC. Every specimen behaves, as illustrated in Fig. 2, like rubber vulcanizates. The specimen, 49 50 T. INOUE ET AL. SIS, is the stiffest and most elastomeric, while the specimen, hi-20, is the softest and less elastic showing rather low stress of leveling off and lacking the rapid re-increase of the stress at higher elongations. It is noted that the SIS, whose styrene content is 23 wt%, has higher initial Young's modulus and larger tensile strength than the hsS-20, whose styrene content is 36 wt% in total.
T ~ (b) hi-20 ,~ . ~' •• . j ) (c) hsS-20 . (d) SIS I Fig. 1. Electron micrographs of ultrathin sections of film specimens 1----1 Jl Specimen hsS-20 is a binary mixture of 80 wt% SI and 20 wt% PS. As seen in Fig. l-c, PS is solubilized, in contrast, into the spherical domains of styrene block of the copolymer SI, which enlarges the size of the spherical domains when compared with Fig. I-a. (9) The domain structure of SIS (Fig. I-d) may be characterized as spheres of styrene component dispersed in a matrix of isoprene component, and some of these spheres are interconnected to form short rodlike domains.
Before drying. In some areas the size of the striped regions was enlarged while in other areas the patterns were confined to spherical identities suspended in a polystyrene matrix. When the film was dried in the ultrasonic field some of these identities appeared to be disintegrating into short rods and spheres of polybutadiene in a polystyrene matrix. These copolymer structures appear to disintegrate with great reluctance. Often the morphology of block copolymer films can be predicted with confidence, but in some cases the structures observed in the electron microscope were not as anticipated.