title: Revealing the morphological architecture of a shape memory polyurethane by simulation.
abstract: The lack of specific knowledge of the network structure in shape memory polymers (SMPs) has prevented us from gaining an in-depth understanding of their mechanisms and limited the potential for materials innovation. This paper firstly reveals the unit-cell nanoscale morphological architecture of SMPs by simulation. The phase separated architecture of a segmented shape memory polyurethane (SMPU) with a 30 wt% hard segment content (HSC, 4,4'-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BDO)) showing good shape memory properties was investigated by dissipative particle dynamics (DPD) simulations. A linked-spherical netpoint-frame phase of MDI, a matrix-switch phase of polycaprolactone (PCL) and a connected-spider-like interphase for BDO were obtained for this SMPU. The BDO interphase can reinforce the MDI network. Based on these simulation results, a three-dimensional (3D) overall morphological architectural model of the SMPU can be established. This theoretical study has verified, enriched and integrated two existing schematic models: one being the morphological model deduced from experiments and the other the frame model for SMPs reported before. It can serve as a theoretical guide for smart polymeric materials design. This method for the simulation of polymer structure at the nanoscale can be extended to many areas such as photonic crystals where nanoscale self-assembly plays a vital role.
authors.affiliation: Institute of Textiles and Clothing, the Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China; The Hong Kong Polytechnic University Shenzhen Base, Shenzhen, China.
authors.forename: Jinlian
authors.initials: J
authors.lastname: Hu
authors.affiliation: Institute of Textiles and Clothing, the Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China; The Hong Kong Polytechnic University Shenzhen Base, Shenzhen, China.
authors.forename: Cuili
authors.initials: C
authors.lastname: Zhang
authors.affiliation: School of Textiles and Clothing, Wuyi University, Jiangmen, Guangdong, 529020, China.
authors.forename: Fenglong
authors.initials: F
authors.lastname: Ji
authors.affiliation: Department Applied Mathematics, the Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
authors.forename: Xun
authors.initials: X
authors.lastname: Li
authors.affiliation: Institute of Textiles and Clothing, the Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China; The Hong Kong Polytechnic University Shenzhen Base, Shenzhen, China.
authors.forename: Jianping
authors.initials: J
authors.lastname: Han
authors.affiliation: Institute of Textiles and Clothing, the Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China; The Hong Kong Polytechnic University Shenzhen Base, Shenzhen, China.
authors.forename: You
authors.initials: Y
authors.lastname: Wu