Melt-crystallized nylon-6 nucleated by the constrained chains of its non-stoichiometric cyclodextrin inclusion compounds and the nylon-6 coalesced from them
Melt-crystallized nylon-6 nucleated by the constrained chains of its non-stoichiometric cyclodextrin inclusion compounds and the nylon-6 coalesced from them
复制标题
DOI：
10.1016/j.polymer.2010.12.049
复制
发表时间：
2011-02-17
期刊：
影响因子：
4.6
通讯作者：
Tonelli, A. E.
中科院分区：
文献类型：
--
作者：
Mohan, A.;Gurarslan, A.;Tonelli, A. E.
Non-covalently bonded crystalline inclusion compounds (ICs) have been formed by threading host cyclic starches, cyclodextrins (CDs), onto guest nylon-6 (N-6) chains. When excess N-6 is employed, non-stoichiometric (n-s)-N-6-CD-ICs, with partially uncovered and "dangling" N-6 chains, result. While the host crystalline CD lattice is stable to similar to 300 degrees C, the uncovered, yet constrained, portions of the N-6 chains emanating from the CD-IC surfaces may crystallize below, or be molten above 225 C, and confer upon them shape-memory. When heated between the T-m of N-6 and the decomposition temperature of the (n-s)-N-6-CD-IC, they may be deformed into a new shape, which is retained following a rapid quench below T-m. When this newly-shaped sample is heated above the T-m of the un-included and crystalline portions of N-6, it reverts back to its original shape in response to the constraining CD-IC crystals.When added at low concentrations, the non-toxic (n-s)-N-6-CD-ICs serve as effective nucleating agents for the bulk crystallization of N-6 from the melt. This is a consequence of the ability of the N-6 chains protruding from their (n-s)-CD-ICs to crystallize more rapidly and at higher temperatures than bulk N-6 chains when their molten mixture is cooled, thereby providing finely dispersed crystalline nuclei for the subsequent crystallization of the bulk N-6 chains. Melt-crystallized N-6 nucleated with (n-s)-N-6-CD-ICs have finer grained more homogeneous morphologies than un-nucleated N-6 samples. Furthermore, N-6s coalesced from their CD-ICs by appropriate removal of the host CD are also found to effectively nucleate the melt-crystallization of bulk N-6, even after long periods of annealing above the T-m of N-6. N-6 coalesced from stoichiometric CD-ICs, with full N-6 coverage, and from (n-s)-N-6-CD-ICs, with only partial N-6 coverage, show very similar crystallization behaviors and both are effective as nucleants, and this is reflected by their higher densities and improved mechanical properties. (C) 2010 Elsevier Ltd. All rights reserved.
