Poly from melt

An overview of the synthesis and characterization of a unique class of polymers with a phosphorus-nitrogen backbone Is presented, with a focus on poly(dichloro-phosphazene) as a common Intermediate for a wide variety of poly(organophosphazenes). Melt and solution polymerization techniques are Illustrated, Including the role of catalysts. The elucidation of chain structure and molecular weight by various dilute solution techniques Is considered. Factors which determine the properties of polymers derived from poly(dichlorophos-phazene) are discussed, with an emphasis on the role that the organic substituent can play In determining the final properties. 

Dynamics of Poly(oxyethylene) Melts Comparison of 13C Nuclear Magnetic Resonance Spin-Lattice Relaxation and Dielectric Relaxation as Determined from Simulations and Experiments. 

Several of the described eondis phases are CD glasses (Sect. 4.2-4 ami 4.6) with different paths into the glassy states. Some of these CD glasses seem to have no corresponding, stabte eondis phase, but are produced as intermediates in the path from melt to stabte erystal [polypropylene]. The ferroelectric effect of poly(vinylidene fluoride), polytrifluOToethylene and its copolymers seems coimected to eondis glass and disorder transitions (Curie temperatures). Condis states seem also to have enhanced chain mobility on mechanical (teformation. 

Hgure 1. Hole fraction h as function of (scaled) temperature for 2 poly(vinylacetate) melts and their glasses formed under pressures of 1 and 800 bar. Black circles, equation 2 , open circles, equation 2 for melt and approximation for glass (see text). Horizon lines mark the magnitude of h at Tg, as dnived from melt theory. Reproduced from ref. 8. Copyright 1977 American Chemical Society. 

Figure 10-12. Melting behavior of a poly(ethylene) as a function of the morphology and the rate of heating. L, Lamellar single crystals from solution D, dendrites obtained by shock cooling solutions Sq spherulites obtained by shock cooling melts under normal pressures Sc, spherulites produced by crystallization under normal pressures E, extended chain crystals obtained by crystallization from high molar mass Eh and low molar mass Em poly(ethylene) melts under high pressures (after B. Wunderlich).

Tsuji, H. and Ikada, Y. (1995) Blends of isotactic tmd atactic poly(lactide)s. I. Effects of mixing ratio of isomers on crystallization of blends from melt. Journal of Applied Polymer Science, 58, 1793-1802. 

Su, ]., Chen, Y., and Tan, L. (2009) Preparation and hydrolytic degradation of poly(hexylene terephthalate-co-lactide) co-polyesters from melting polycondensation. /. Biomater. Sci, 20, 99. 

Bao, R.-Y., Yang, W., Wei, X.-F., Xie, B.-H., Yang, M.-B., 2014. Enhanced formation of stereocomplex crystallites of high molecular weight poly(L-lactide)/poly(r>-lactide) blends from melt by using poly(ethylene glycol). ACS Sustainable Chemistry Engineering 2, 2301-2309. 

Thakur and Meyler [22] have reported the growth of thin-film single crystals of poly(diacetylenes) by a shear process that produces aligned areas of about 1 cm-from melts and about 50 mm- from solution. These thin-film crystals were reported to be four orders of magnitude larger than those previously prepared by Isoda [23]. 

In fact, one early problem that continues to plague many studies is that deuterated polyethylene tends to phase-separate from ordinary, protonated polymer, even though they are chemically identical. The cause has been related to slightly different crystallization rates owing to poly-deuteroethylene melting 6°C lower than ordinary polyethylene. 

Shenoy, A. V., Saini, D. R., and Nadkami, V. M. Rheolo of poly(vinyl chloride) formulations from melt flow index measurements, /. lAnyl TedmoL 5,192—197 (1983). 

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