Block copolymers copolyamides

Block coal, 6 705 Block copolyamide, 79 739 Block copolymerization, 79 762 Block copolymers, 7 645-650 70 436 23 367... 

Simple melt blending reactions can also be applied to preparations of block copolyamides, similarly to the process for polyesters, th time, total equilibrium conditions also are gradually achieved in the melt. Interfacial polycondensation is also useful in preparation of block copolymers. When mixed diacid chlorides and/or mixed diamines are reacted, the more active diacid chlorides and/or diamines react preferentially and blocks form. In addition, it is possible to carry out the growth of one of the segments first, to a fairly large size, and follow it by addition of the other comonomers. ... 

Adventitious routes to partially blocky copolyamides have been mentioned in an earlier section, and block copolymer syntheses by conventional random block copolymerization and by oligomer combination reactions are summarized in Tables 3 and 4. It should be noted that the high melting points and restricted solubilities which are the source of useful properties in intermolecularly hydrogen-bonded polyamides and analogous polymers are also a frequent source of practical difficulties in the preparation of their block copolymers. 

MasaY B, Cefelin P and Sebenda J (1979) Block copolymers of Copolyamides with polyoxirane, J Polym Sci Polym Chem Ed 17 2317-2335. 

By using mixtures of adipic and azelaic acids as monomers in the reaction with MDI, transparent copolymers are obtained useful as engineering thermoplastics. Also, copolyamides obtained from mixtures of isophthalic (IPA) and azelaic acids and MDI/TDI mixtures have been made. TDI in combination with MDI is used to lower the melt temperature of the IPA/MDI blocks to allow thermoplastic processing. 

Homopolymers derived from MDI and azelaic acid are semicrystalline engineering plastics with a Tg of 135°C and a Tm of 290°C (88). Copoljrmers of MDI with azelaic acid, containing 20-30 mol% of adipic acid show a eutectic Tm of approximately 240°C. These amorphous or slightly crystalline copolymers have mechanical properties comparable to transparent nylons or polycarbonates. Although injection molded samples are transparent, they will crystallize and turn opaque. Copolyamides derived from MDI and aromatic dicarboxylic acids are more difficult to prepare. Because of the very high Tm (420°C) of the isophthalic acid/MDI block it was necessary to prevent the formation of any appreciable ciystalline blocks, which was accomplished by prereacting a portion of the isophthalic acid (15-20 mol%) with 2,4-TDI. In this manner crystallization of the isophthalic acid/MDI blocks was surpressed (89). Thus, copolyamides containing IPA/azelaic acid (50 50) are obtained with thermal and mechanical properties similar to poly-sulfone. 

There is still much interest in nylon 6 derived by classical polycondensation and lactam ring-opening routes. In addition, in the past few years interest has centred on the synthesis and characterization of aromatic polyamides for use as high temperature materials and for their liquid crystal properties. In addition, work on copolyamides has also been growing with emphasis on block and graft copolymer systems containing aromatic amide blocks. 

Block and graft copolymer systems have also invoked interest with studies on poly(m-phenylene-isophthalamide)-fe-ethylene oxide or -h-dimethylsiloxane systems where conditions have been established for (AB) and triblock ABA and BAB synthesis. Poly(m-phenylene-isophthalamide) has been grafted with acrylonitrile following metallation in liquid ammonia. Regular copolyamide sequences have been prepared by a two-stage low-temperature solution polymerization yielding biphenylene terephthalamide-adipamide and dimethyl piperazine terephthalamide-adipamide copolymers. The preparation of regular aliphatic-aromatic copolyoxamides from diamine-oxamides and aromatic diadd... 

The work by Ciferri and coworkers [128-130] focused on the supramolecular organization of aromatic rod-coil copolyamides in diluted (isotropic) and moderately concentrated (lyotropic) phases. Their diblock copolymers were based on a rigid block of poly(p-benzamide) (PBA) having a DP about 100, and different comparable lengths of flexible blocks, such as poly(m-phenylene isophthalamide) (MPD-I), poly(/n-benzamide) (MBA), or poly(ethylene glycol) (PEG). The use of end-capped prepolymers and selective extraction techniques assured a strict two-block sequence, the absence of free homopolymers not strongly bound to the copolymers, and a fractionation in terms of the rigid/flexible compositional distribution ratio. 

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