Universal Effects of Chirality on the Self-Assembly of Block Copolymers and Polymers

2019年04月10日

报告题目:Universal Effects of Chirality on the Self-Assembly of Block Copolymers and Polymers

报告人:Prof. Rong-Ming Ho, Department of Chemical Engineering, National Tsing Hua University, Hsinchu 30013

时间:2019-04-18 10:00

地点:卢嘉锡楼202报告厅

报告摘要:

Here, we aim to investigate the universal effects of chirality on the self-assembly of chiral block copolymers (BCPs*). Poly(cyclohexylglycolide) (PCG)-based BCPs* (i.e., poly(benzyl methacrylate)-b-poly(D-cyclohexylglycolide) (PBnMA-PDCG) and PBnMA-b-poly(L-cyclohexyl glycolide) (PBnMA-PLCG)) have been synthesized for self-assembly to give systematic comparisons with polylactide (PLA)-based BCPs* with respect to the chirality effects on BCP self-assembly. Opposite handedness of PCG helical chains in the enantiomeric BCPs* were identified by the vibrational circular dichroism (VCD) results of carbonyl group (C=O) stretching due to intra-chain chiral interactions of constituted chiral entities. By taking advantage of inter-chain chiral interactions as evidenced by the VCD results of C-O-C vibration, the self-assembly of the PCG-based BCP* gave the formation of helical phase (H*) with preferential handedness of helical microdomain as recognized by transmission electron microscopy tomography (3D TEM), suggesting the chirality effects on BCP self-assembly and the homochiral evolution from molecular to hierarchical scales. With higher twisting power than that of PLA-based BCPs*, the thermodynamic stability of forming H* in the PCG-based BCPs* can be significantly enhanced. The observed phase behaviors of the PCG-based BCP*s are in line with theoretical prediction based on chiral orientational self-consistent field theory at which the chiral PCG behaves like mesogenic liquid crystal as predicted by theory and evidenced by the appearance of VCD signals of the C-O-C vibration. For chiral polylactides, twisted lamellae in crystalline banded spherulite could be formed by dense packing scheme and effective interactions upon helical chains from self-assembly. The handedness of the twisted lamella can be determined by using rotation experiment of polarized light microscopy (PLM). Similar to the self-assembly of BCPs*, the examined results suggest the homochiral evolution in the crystallized chiral polylactides. The suggested methodologies for the understanding of the mechanisms of the chirality transfer at different length scales provide the approaches to give supplementary information for disclosing the mysteries of the homochiral evolution from molecular level.

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Figure. Homochiral evolution from the self-assembly of chiral and block copolymers and polymers.

(Ho, R. M. et al. Acc. Chem. Res. 2017, 50, 1011.)


报告人简介:

Name: Rong-Ming Ho

Affiliation: Department of Chemical Engineering National Tsing Hua University

Position: Chairman and NTHU Chair Professor

Address: No. 101, Section 2, Kuang-Fu Road, Hsinchu,Taiwan 30013, R.O.C.

E-mail: rmho@mx.nthu.edu.tw


Education:

1991/09- 1995/05  Ph.D.  Institute of Polymer Science, University of Akron, USA


Academic Appointment:

Present  NTHU Chair Professor  Department of Chemical Engineering,National Tsing Hua University, Hsinchu, Taiwan

2006 – 2009  Professor  Department of Chemical Engineering National Tsing Hua University, Hsinchu, Taiwan

2002 – 2006  Associate Professor  Department of Chemical Engineering,National Tsing Hua University, Hsinchu, Taiwan


Research Interests:

Research focuses in recent ten years:

Self-assembly of chiral polymers and block copolymers

Fabrication of well-ordered nanohybrids and nanoporous materials

Nanopatterning Technologies from Bottom-up Methods


Awards:

Outstanding Research Award, Polymer Society of Taiwan, 2015

Fellow of American Physical Society, 2014

Outstanding Research Award, Ministry of Science and Technology of Taiwan, 2013

Member of Editorial Advisory Board for Macromolecules 2014-2016

Member of Editorial Advisory Board for ACS Macro Letters 2014-2016

DPS Outstanding Alumni Award, University of Akron, 2012

Outstanding Research Award, National Science Council of Taiwan, 2006