Studies of shape memory polymers with novel functions

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Studies of shape memory polymers with novel functions

 

Author: Wu, You
Title: Studies of shape memory polymers with novel functions
Degree: Ph.D.
Year: 2015
Subject: Shape memory polymers.
Smart materials.
Shape memory effect.
Hong Kong Polytechnic University -- Dissertations
Department: Institute of Textiles and Clothing
Pages: xvii, 177 pages : color illustrations
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2828513
URI: http://theses.lib.polyu.edu.hk/handle/200/8269
Abstract: Shape memory polymers (SMPs) are a class of smart materials whose shape could change with external stimuli. They have been widely used in terms of form, stimuli,structure and applications. Recently, developing SMPs with additional functions has drawn increasing attention. This project is focused on the research of functional SMPs with novel molecular strategies, including multi-responsive chromic behavior, stress-free two way shape memory effect, light/heat dual sensitive triple shape memory effect and supra-SMPs with moisture management applications. A new multi-functional SMP which can memorize both shapes and colors responsive to different stimuli by was fabricated by covalently connecting the aggregation induced emission (AIE)-active dye to a polymer. The color of the polymer is responsive to its memory properties such as the original and temporary shapes,shape recovery, associated stimuli including solvent and transition temperature. The outcome polymer displayed excellent shape memory effect and fluorescent response to mechanical stress, temperature and solvent. Furthermore, a new molecular strategy for two-way shape memory polymers (TWSMPs) was studied. TWSMPs or reversible shape memory polymers are one of the most promising smart materials because of their potential applications as artificial muscle, actuators, sensors etc. None of current methods could realize reversible shrinkage without external tensile at ambient temperature. It is hoped that the issue can be solved by a simple method, which is employing an interpenetrating polymeric network (IPN) with elastomeric network and crystalline network. Thus, a series of polymers with UV-crosslinked crystalline segment and thermal-crosslinked elastomeric segment as IPNs were constructed and their possibilities for two-way shape memory effect were further explored. This work demonstrated a simple way of fabricating stress-free TWSMPs with Ttrans around 40 °C and a maximum shape changing ratio around 6% (close to shape memory alloy). In addition,a facile approach was employed to fabricate Light/heat dual-responsive triple shape memory polymer (SMP) by simply mixing Zn(Mebip)₂(NTf₂)₂, a metallosupramolecular unit formed by coordinate 2,6-bis(N-methyl benzimidazolyl)-pyridine (Mebip) ligands to Zinc di[bis(trifluoromethylsulfonyl)-imide] (Zn(NTf₂)₂), or Gold Nanoparticles (AuNPs) into one part of epoxy resin. Also thanks to the light-heat transfer nature of Zn(Mebip)₂(NTf₂)₂ and segmented material structure,the outcome polymer displayed UV sensitivity to composite part, while leaving the shape of neat SMP part unchanged under UV source (solely thermal sensitive). Later, a series of SMPs with supra-molecular switches were fabricated by employing pyridine into polymer backbone as proton acceptors.Varies proton donors, like the neat SMPs and poly(4-vinylphenol) were blended into the supra-SMPs. Unlike previously reported thermal responsive water vapor permeability, the current work was focused on the moisture responsive water vapor permeability. The out-come Supra-SMP displayed RH-dependent WVP behavior, which is, at low RH,the Supra-molecular switches are closed, leading to a low WVP.When at high RH(say, higher than 65%), the WVP of the supra-SMPs increased dramatically. The mechanism of moisture sensitive WVP was further proved by FTIR. Such RH dependent WVP displayed the potential applications as moisture management materials in packaging and textiles industrials.

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