Polymer Nucleation via Segmental Bundling

趙君聖(Chun-Sheng Chao)

指導教授 ： 蘇安仲

國立清華大學/工學院/化學工程學系/碩士(2009年)

摘要

Many phenomena observed in nucleation and growth of polymer crystals from the melt state remained unexplained by classical theories in terms of chain length dependence and fractionation effects. Also unexplained are morphological features of nanometer-sized nodules in melt-crystallized polymer crystals. Here we develop a molecular theory in terms of nanograin nucleation as bundled segments; this may then serve as the basis to describe the growth and coalescence of polymer crystals during cold crystallization. In our model, each bundle is composed of a limited portion of segments which may not all belong to one polymer chain, forming tight and loose loops and ordered stems; this allows for quantitative analysis via standard statistical mechanics. The model predicts increased strains around each nanograin during growth and (even more strongly) upon coalescence, the size of nanograins is therefore predicted to be limited at a given temperature as experimentally observed. It also predicts an upper temperature above which the coalesced nanograins are no longer capable of further coalescence. Qualitatively, the strain field developed around a nanograin is expected to result in an effective exclusion zone (reminiscent of brushes around micelles) that explains the experimentally observed FCC-like arrangement of nanograins during polymer cold crystallization. With the main feature of the balance between crystallization and elastic forces duly considered, this single-chain model appears to serve well as a simplified basis for the description of polymer crystallization in terms of multi-chain nanograins as units of morphological development.

關鍵字

高分子結晶 ； 冷結晶 ； 成核 ； 束狀核 ； 奈米晶粒 ； 聚合

並列摘要

無資料

並列關鍵字

polymer crystallization ； cold crystallization ； nucleation ； bundle ； nanograin ； coalescence

參考文獻

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