Anisotropic Nucleation and Janus-Faced Crystals of Poly(l-lactic acid) Interacting with an Amorphous Diluent

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• 作者：Eamor M. Woo ; Hikmatun Ni鈥檓ah ; Yu-Hsiang Wang
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2014
• 出版时间：June 11, 2014
• 年：2014
• 卷：53
• 期：23
• 页码：9772-9780
• 全文大小：575K
• 年卷期：v.53,no.23(June 11, 2014)
• ISSN：1520-5045

文摘

Atomic-force microscopic and X-ray techniques were applied to reveal and analyze uniquely three types of distinctly different crystals, including a Janus-face composite type of spherulites in LM_w-PLLA induced by mixing with aPMMA (20 wt %). One type (Type-1) is completely packed by fibrous lamellae, while the second type (Type-2) is completely packed by flat-on platelet crystals; and the third type, a dual-faced (i.e., Janus-faced 鈥?Type-3) spherulite with two distinguished patterns filling the composite spherulite鈥檚 perpendicular quadrants that is originated from sheaf-like directional growth from nuclei to pack into fibrous lamellae, while the perpendicular growth was diffusion-drained leading to thinner flat-on platelets. The Janus-face spherulite type (half-and-half fibrous lamellae and flat-on platelets) became more significant only when the 80/20 mixtures were melt-crystallized at T_c = 110鈥?15 掳C. That is, existence of Type-3 Janus-faced spherulite is composition- and temperature-selective for favorable nucleation and growth. Mechanisms leading to such diversified patterns and Janus-face spherulites in the LM_w-PLLA/aPMMA blend were probed.