A new family of the thermo-responsive polymers based on poly[N-(4-vinylbenzyl)-N,N-dialkylamine] with the pendent amine group as well as the doubly thermo-responsive triblock copolymer were synthesized by reversible addition–fragmentation chain transfer (RAFT) polymerization. These polymers showed the lower critical solution temperature (LCST) and/or the upper critical solution temperature (UCST) in alcohol and in the alcohol/water mixture. The polymer molecular weight, the polymer concentration, the cosolvent/nonsolvent and the deuterated solvent affecting the LCST and/or UCST were investigated, and their great influence on the LCST/UCST was demonstrated. The origin of the phase transition of poly[N-(4-vinylbenzyl)-N,N-dialkylamine] at LCST upon heating was investigated and the possible reason was proposed. The doubly thermo-responsive triblock copolymer of PVMA53-b-PVEA108-b-PVMA53 underwent phase transition at two LCST temperatures. The PVEA108 block underwent the initial phase transition at the first LCST of 32.5 °C to form core–corona micelles, and then the subsequent phase transition of the PVMA53 block took place at the second LCST of 54.5 °C to produce corona-collapsed micelles. The proposed polymers based on poly[N-(4-vinylbenzyl)-N,N-dialkylamine] are anticipated to broaden the thermo-responsive polymer range and will be useful in polymer science.
Long Bai,Yong Jin,Xiang Shang,Hongyu Jin,Wenhua Zeng,Liangjie Shi
Despite the current progress in thermo-responsive materials, it is still a significant challenge to develop superior multiple temperature-sensitive ionic conductive hydrogels with programmable regulation capability for interactive wearable iontronics. Here, a dual thermo-responsive ionic conductive hydrogel (DTICH) is constructed based on a salt modulation strategy, which cleverly integrates low-temperature sensitive sodium dodecyl sulfate (SDS) and high-temperature sensitive poly( N -isopropylacrylamide) PNIPAm-based polymer. Owing to the common ion effect and salting-out effect, the resultant DTICH hydrogel visually presents wide and tunable dual temperature response behaviors of 0-18℃ (T k ) and 37-80℃ (LCST) by controlling NaCl concentration for the first time. Meanwhile, benefiting from the synergy of NaCl and thermo-sensitive materials, the hydrogel is concurrently endowed with excellent stretchability (>900 %), adhesion (adhesion strength >30 kPa), frost resisting (-40℃) and multilevel encryption functions. More importantly, the DTICH hydrogel can ingeniously perceive mechanical force and external temperature via the changes of relative resistance and transparency, which can be applied as human–computer interfaces to interactively monitor human motions and temperatures in real time. Therefore, our study establishes a brand new and effective route for the rational design and fabrication of high-level visual interactive devices and smart wearable iontronics.
Lan Feng,Qin Chen,Huitong Cheng,Qiao Yu,Weifeng Zhao,Changsheng Zhao
Incomplete contact between a pre-formed hydrogel and irregular wound limits the therapeutic effect of the dressing and increases the risk of infection; while great concerns have remained regarding the potential toxicity of the residual additives of chemical crosslinking for in situ forming hydrogels. Therefore, it is desirable to develop a self-adaptive hydrogel in response to skin temperature with shape adaptability and efficient antibacterial properties to prevent microbial invasion. Herein, a dually-thermoresponsive hydrogel composed of poly( N -isopropylacrylamide) (PNIPAm) and methacrylated κ -carrageenan (MA- κ -CA) is designed with compliance at physiological temperature to realize shape adaptability for completely covering irregular wounds. Furthermore, the hydrogel with near-infrared (NIR)-responsive polypyrrole-polydopamine nanoparticles (PPy-PDA NPs) and Zn 2+ -derived zeolitic imidazolate framework (ZIF-8) can generate localized heat and gradually release Zn 2+ to realize safe, effective synergetic photothermal–chemical bactericidal capability. In addition, the release rate of Zn 2+ can be accelerated by NIR-induced heating, and thus a more efficient sterilization can be provided to severely infected wounds. Therefore, the proposed hydrogel would serve as a promising wound dressing for the full course of wound healing, with the abilities of perfectly covering the wound and adapting to regenerating tissue, and controllable photothermal-chemical antibacterial capability to reach high bactericidal efficiency and long-term release of antibacterial agents.
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