By Maurice Morton (auth.), S. L. Aggarwal (eds.)

Block polymers characterize one other milestone within the guidance of polymers of managed constitution. Catalysts and polymerization equipment that allowed the training of polymers during which the stereo- and geometric isomerism of the monomer devices may be con­ trolled have certainly been one of the significant advancements in polymer technology over the last decade. The synthesis of block polymers, during which the series size of the comonomer devices could be con­ trolled, portends both very important advancements within the technology and know-how of polymers. The papers amassed during this quantity hide basically the professional­ ceedings of the newest symposium on block polymers, backed by means of the department of Polymer Chemistry of the yank Chemical Society. It used to be held in ny urban throughout the Society's 158th nationwide assembly in September, 1969. extra contributions from chosen authors have been invited specially for this publication to accomplish the main up to date account of the advances which were made because the improvement of the thermoplastic elastomers that first introduced into concentration this significant zone of study. the 1st papers during this quantity draw awareness to a number of the difficulties that are supposed to be thought of within the coaching of block polymers of accurately outlined constitution from styrene and butadiene or isoprene by way of anionic polymerization. Characterization of block polymers provides many difficulties and there's a paucity of systematic paintings during this sector. consciousness has been given to the di­ lute resolution houses of block polymers,however, in a single of the papers during this volume.

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Extra info for Block Polymers: Proceedings of the Symposium on Block Polymers at the Meeting of the American Chemical Society in New York City in September 1969

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A typical example of the effect of heating rate is shown in Figure 5 for homopolybutadiene (B). We note that the relative heat capacity change (1\) decreases as the heating rate decreases and extrapolates to a zero value at zero heating rate. Likewise, the measured glass transition temperature R. IKEDA, M. L. WALLACH, AND R. J. ANGELO 48 decreases with decreasing heating rate, and with homopolybutadiene extrapolates to a Tg value of -5°C. at an infinitely slow heating rate. ( The effects of heating rate are in accord with published results 6).

TABLE II Bragg Distances from Different S-B-S Polymers MW (S-B-S) 21,100-63,400-21,100 13,700-63,400-13,700 8,200-63,400- 8,200 % styrene 40 30 20 Bragg Distance(R) 430 339 325 Homopolymer-Tri-Block Polymer Blends Homopolymer of polystyrene (MW 15,000) was added to the THF casting solution of the tri-block polymer (S-I-S 14,000-109,000-14,000) in varying amounts [5J. The films were examined by x-ray scattering and the data are plotted in Figure (3). The Bragg distances vary by 30%, being larger the greater the amount of homopolymer added.

These results are indicative of very little composition heterogeneity and we concluded, therefore, that the polymers are genuine block copolymers with insignificant 47 MULTIPLE GLASS TRANSITIONS OF BLOCK POLYMERS quantities of homopolymer contamination. 4 {l o >c 2 ..... --~o~------~o~--------~no~~o~ o -4 -2 liS - lie o 2 II Figure 4. Apparent Molecular Weight vs. Refractive Index Increment Variable; Vs is an/dc of homopolystyrene, '13 is the an/dc of homopolybutadiene and v is the an/dc of the copolymer S/B2.

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