6月11日高分子科学系列讲座预告

报告题目: Coupled crystallization in a diblock copolymer of lamellar morphology

报 告 人: Dr. Jianjun Xu、

单　  位: DSM Resolve / Research, Netherlands

报告时间: 2012年6月11日（星期一）上午9:30

报告地点: 主楼四楼学术厅(410房间)

附：报告人及报告内容简介

报告题目：Coupled crystallization in a diblock copolymer of lamellar morphology（No. PSLAB136-PS2012-14）

报 告 人：Dr. Jianjun XU

单　　位：DSM Resolve / Research, Netherlands

报告时间：2012年6月11日（星期一）上午9:30

报告地点：主楼四楼学术厅（410房间)

报告内容摘要： Interesting crystallization behaviour in an amorphous-semicrystalline diblock copolymer [1] will be presented. The copolymer locates in weak segregation limit of the phase diagram and has a lamellar morphology. The amorphous block is polystrene (PS) and the crystalline block is poly(ferrocenyl dimethylsilane) (PFS) which has a small driving force for crystallization [1-3]. The contrast in electron densities of the PS and the PFS phases is large and thus the block copolymer is ideal for TEM and in-situ SAXS studies. Isothermal crystallization of the lamellar PS-b-PFS dilock copolymer is shown to proceed in a confined and grain-by-grain fashion. Here a ‘grain’ is defined as an ensemble of stacked lamellae wherein the PFS crystallization was found to spread quickly but stop at its surroundings. The in situ SAXS investigations were only able to resolve partially crystallized grains at very high temperatures. In all other cases, the SAXS patterns represent superposition of the scattering features of either fully amorphous or fully crystallized grains. We assume that one single nucleation event is sufficient to induce rapid crystallization of the whole grain. The high rate of crystal growth within a grain – in combination with considerable spatial changes associated with the PFS crystallization – indicate that a highly efficient pathway is accessible which allows spreading of the crystallization even perpendicular to the lamella planes, i.e., passing through the amorphous PS layers. We suggest that conformational changes in the PS as induced by the PFDMS crystallization (‘squeezing transfer’) are responsible for this fast spreading of the crystallization in the grain. The process is thus called ‘coupled crystallization’. References: [1] J. Xu, V. Bellas, B. Jungnickel, B. Stühn, M. Rehahn. Macromol. Chem. Phys. 2010, 211, 2276. [2] J. Xu, V. Bellas, B. Jungnickel, B. Stühn, M. Rehahn. Macromol. Chem. Phys. 2010, 211, 1261. [3] J. Xu, Y. Ma, W. Hu, M. Rehahn and G. Reiter. Nature Materials. 209, 8, 348.

报告人介绍

Dr. Jianjun XU

Jianjun Xu is senior scientist at DSM Resolve in DSM Material Science Research Campus in the Netherlands. He obtained PhD in Polymer Chemistry in Institute of Chemistry, Chinese Academy of Sciences in 1998, in group of Prof. Yunzhao Yu. From 1998 to 2001, he worked at ICCAS, as assistant professor and later as associate professor. From 2001 to 2008, he stayed in Deutsches Kunststoff-Institut in Darmstadt, Germany, first as postdoc in physics department (with PD Ingo Alig), and later as scientist in polymer chemistry (with Prof. Matthias Rehahn) and applied polymer physics. In April 2008, he joined DSM in the Netherlands as scientist in the X-ray lab, and now as senior scientist. He is responsible in the lab for DSM-part of the activities. His research experience is diverse, including epoxy resin, polyurethane, polymer blend, block copolymer, semi-conducting polymer, polyamide film and polyethylene fibers.

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