Dual-response of temperature and humidity asymmetrical cotton fabric prepared based on thiol-ene click chemistry
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Ene reaction
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Thermo-sensitive poly(N-isopropylacrylamide)(PNIPAAm) hydrogel was prepared by free-radical in water.With hydrophobic ibuprofen(IBU) as mode drug,the thermo-sensitive property of PNIPAAm and interaction with IBU were studied.The IBU release behavior was investigated in phosphate buffer solution(PBS,pH 7.4) at different temperatures(25 ℃ and 37 ℃).It was found that a lower critical solution temperature(LCST) of PNIPAAm around 33 ℃ and interacted with IBU by intermolecular hydrogen bond.The IBU released slower at 37 ℃(above LCST) than at 25 ℃ (bellow LCST) in PBS.Therefore,the release of IBU from the thermo-sensitive PNIPAAm hydrogel could be controlled by changing the temperature around LCST.
Poly(N-isopropylacrylamide)
Phosphate buffered saline
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Copolymerization between bacterial cellulose nanocrystal (CN) and methyl cellulose (MC) was carried out using UV light to produce a biocompatible hydrogel at body temperature and liquid at room temperature. Viscosity and salt effect of the MC and copolymer solution at room temperature and its Lower Critical Solution Temperature (LCST) were evaluated. The analysis showed that the higher concentration of methyl cellulose and salt content in the solution produced lower LCST and higher solution viscosity. All samples of polymer solution with MC concentrations of 1 and 2% have a viscosity less than 5000 cP at room temperature. The solutions with MC concentration of 1, 2, and 3% have respectively LCST of 59, 58, and 57°C, while its copolymer solutions with CN concentration of 0.1, 0.3, and 0.5% have respectively LCST of 55, 51, and 41°C. The salt addition to the solution of MC-CN copolymer with concentrations of 1x and 1.5x Phosphat Buffered Saline (PBS) produces respectively LCST of 47 and 38°C. The results suggest that the copolymer solution of MC-CN could produce a lower LCST and the addition of salt could amplify the effect of LCST decrease that can be used to produce a biocompatible hydrogel with LCST as close as body temperature.
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Poly(N-isopropylacrylamide)(PNIPAm) and P(NIPAm-co-KYD) copolymer exit a lower critical solution temperature(LCST) in aqueous solution which is about 33℃,14℃ and 4℃,respectively.The effect of one or multi-factor(additions) on LCST of PNIPAm or P(NIPAm-co-KYD) aqueous solution,such as cationic surfactant(CTAC),EDTA,salt or ionic/nonionic polymer were studied in this paper.It was found that the LCST decreased to 25℃ abruptly when the concentration of EDTA was 0.1% in the system in the absence of CTAC.With further increase in concentration of EDTA,the LCST changed more slowly 2℃ than before.However,the effect of CTAC differed greatly from EDTA.The phenomenon of polymers coil-to-globe transition was no longer clear in the system containing 0.5-1.0% CTAC and there was a little decrease in LCST when higher than 1.5%,accompanying the clear phase transition again.Salt could make the LCST of the system drop in line,which was meaningful as guidance in theory.It was found that changes of LCST were mild as we studied the effect of multi-factor on LCST.
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Cationic polymerization
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Although the gelation process and lower critical solution temperature (LCST) behavior are well acknowledged in polymer systems, low-molecular-weight gelators (LMWGs) rarely display LCST behavior during supramolecular gelation. Herein, we report an LMWG system with LCST-type thermoresponsiveness and an LCST-triggered supramolecular gelation process. Temperature plays a crucial role in this system, not only affecting the LCST phase separation but also triggering the gelation process. The backbones (three-dimensional structures) of the resulting hydrogel are the hierarchical assemblies of the LMWG undergoing the LCST phase separation. Hence, the gelation of the LMWG is only realized when the gelation temperature is above the critical transition temperature (Tcloud) of the LCST behavior, which is different from many supramolecular or polymeric hydrogel systems.
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Thiol-ene reactions are most commonly photoinitiated and generally utilize a stoichiometric reaction mixture of thiols and enes. The radical initiated thiol-ene reaction is unique in that it is the only known radical step growth polymerization. Thiol-ene systems have significant advantages over acrylic polymerizations in that they are relatively insensitive to oxygen inhibition and exhibit significantly lower levels of shrinkage and stress. These properties along with many more that are highlighted in this chapter have led to thiol-ene systems being the focus of extensive research and development efforts for applications in biomaterials, nanotechnology, and numerous other high-performance polymers. Regardless of the reaction conditions or mechanism, the thiol-ene reaction results in the anti-Markovnikov addition of a thiol to an ene functional group. The chapter also discusses the chemoselectivity and side reactions as well as the applications and representative examples from the literature of thiol-ene systems.
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Abstract A novel hyperbranched lower critical solution temperature (LCST) polymer with sharp temperature and CO 2 ‐responsive behaviors is presented in this study. The target polymer of hyperbranched poly(oligo(ethylene glycol) (HBPOEG) is constructed using POEG as the backbone and tertiary amines as branch points. Phase transition of HBPOEG in aqueous solution is investigated by heating and cooling the system; the results indicate that HBPOEG in aqueous solution has a concentration‐dependent phase transition behavior with excellent repeatability. Moreover, LCST of HBPOEG can be tuned by bubbling CO 2 into the solution, as the tertiary amines can be protonated and the solubility of the polymer would increase by bubbling CO 2 into the system, leading to an increase of LCST of the polymer. Further bubbling N 2 to remove CO 2 can reversibly turn back the LCST to its original value. This backbone‐based hyperbranched LCST polymer with both CO 2 and temperature responsiveness can be applied in application areas like drug delivery, gene transfection, functional coatings, etc.
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Abstract The copolymers of N,N-diethylacrylamide and ovomucoid from duck egg white (an inhibitor of proteolytic enzymes) with low critical solution temperature (LCST) have been synthesized. The behaviour of these copolymers at the point of phase transition was investigated. It was shown that the relation between LCST and physiological activity for these copolymers is a function of their composition. The increase of ovomucoid content leads to the increase of LCST. When the content of ovomucoid rises above 0.2 mol%, LCST disappears. At the same time the physiological activity of obtained copolymers decrease with increasing of N,N-diethylacrylamide content. Keywords: LOW CRITICAL SOLUTION TEMPERATUREPOLYMERIC CARRIERSPHYSIOLOGICAL ACTIVITYPHASE TRANSITIONDRUG TARGETING
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