Dielectric relaxation spectroscopy (DRS) was used to investigate the effect of morphological evolution on conductivity behavior of PLA/PCL blends containing P[MPEGMA-IL]. The morphology of blends changes from sea-island morphology into co-continuous morphology with increasing P[MPEGMA-IL] content. P[MEPGMA-IL] could mainly localize in PCL domains and expand to the interface layer between the PLA and PCL phase because of the low viscosity of PCL phase and the high affinity of MEPGMA groups for both polymer phases. The dielectric results were discussed in terms of α relaxation that corresponds to normal and segmental mode movement, interfacial polarization that corresponds to interfacial aggregation of charge carriers, and ac conductivity that originates from conductive network of mobile charge carriers. Co-continuous morphology and high ions concentration lead to the enhancement of segment movement and ion conductive channel in PCL phase, which correspond to high conductivity and low activation energy of PLA/PCL/8P[MEGMA-IL] blend.
It is valuable research to improve the compatibility and toughness of PLA/PCL blends while endowing them with shape memory & 4D printing capability. In this work, lactic acid/caprolactone-modified chitosan (mCS) was used to connect the amorphous region of PLA and PCL to achieve compatibilisation, toughening and 4D printing shape memory ability. The effects of different mCS additions on the morphology, crystalline behaviour, and thermal properties of PLA/PCL blends were observed to study the mechanism of compatibilisation and toughening. Adding 0.5 g mCS into 10 g PLA/PCL blends had the best compatibilisation and toughening effect. At the same time, the blends with this addition ratio had the best shape memory performance after 4D printing. The shape fixity and shape memory ratios of the 4D printing model were as high as 100% and 94.5%, respectively. This work provides a new way to fabricate biomedical devices and bionic components with 4D printing.
Wang Ping,Zhang Di,Zhou Yiyang,Li Yu,Fang Huagao,Wei Haibing,Ding Yunsheng
A novel biodegradable 1,2,3-triazolium-functionalized PEG- b -PCL copolymer (TAPEC) was synthesized by the “click” coupling of methoxypolyethylene glycol azide and α-propargyl-ω-hydroxyl-poly(ε-caprolactone), followed by the quaternization of the 1,2,3-triazole moiety with iodomethane. All the intermediates and TAPEC were characterized by 1 H NMR, FT-IR, and gel permeation chromatography (GPC). Taking advantage of the characteristics of ionic liquid and block copolymer, this ion-containing diblock copolymer is expected to be used as a novel compatibilizer in mixed biopolyester for regulating the interface and crystallization behaviors. Hence, the TAPEC was evaluated as a compatibilizer and an interface emulsifier in the blends of polylactic acid (PLA) and poly(ε-caprolactone) (PCL). Non-isothermal crystallization experimental results showed that the TAPEC with the higher amount of ε-caprolactone units induces a plasticization and nucleate effect that increased the crystallization ability of the PLA phase; meanwhile, in the PCL phase, the agminated ionic cluster acting as a nucleating agent significantly increased the crystalline of PCL.
Bin Wang,Xin Ye,Bowen Wang,Xiping Li,Shanglin Xiao,Hesheng Liu
Polymer blend nanocomposites with cocontinuous morphology are popular options for realizing various functions, whereas their miscibility and mechanical properties are usually marginalized. Herein, mechanically strong biodegradable nanocomposites were achieved by exploiting the vinyl functionalized graphene (VGN) as a highly efficient compatibilizer for cocontinuous poly (lactic acid)/poly (ε-caprolactone) (PLA/PCL) blends. After being reactively compatibilized using 0.5, 1.0, and 2.0 wt% of VGN, the phase size of cocontinuous PLA/PCL blend was remarkably decreased, and the tensile strength was increased by 200%, 280%, and 253%, respectively. Moreover, the reactively compatibilized PLA/PCL/VGN blend nanocomposites were more ductile than the PLA/PCL blend. Efficient compatibilization and strong interfacial interactions were responsible for the enhanced mechanical properties. The strong interfacial interactions in reactively compatibilized PLA/PCL/VGN blend nanocomposites were evidenced by the linear rheological and atomic force microscopical modulus measuring results. This work provides a facile strategy for compatibilizing and reinforcing biodegradable polymer blend nanocomposites using reactive graphene, which can be potentially used as highly efficient compatibilizers for immiscible biopolymer blends.
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