A new class of thermoresponsive random polyurethanes is successfully synthesized and characterized. Poly(ethylene glycol) diol (Mn = 1500 Da) and 2,2‐dimethylolpropionic acid are reacted with isophorone diisocyanate in the presence of methane sulfonic acid catalyst. It is found that these polyurethanes are thermoresponsive in aqueous media and manifest a lower critical solution temperature (LCST) that can be easily tuned from 30 °C to 70 °C by increasing the poly(ethylene glycol) content. Their sharp LCST transitions make these random polyurethanes ideal candidates for stimuli‐responsive drug delivery applications. To that end, the ability of these systems to efficiently sequester doxorubicin (up to 36 wt%) by means of a sonication/dialysis method is successfully demonstrated. Additionally, it is also demonstrated that accelerated doxorubicin release kinetics from the nanoparticles can be attained above the LCST.
A thermoresponsive poly(NIPAM-co-dye) copolymer with covalently attached D-π-A type dye was prepared by typical radical copolymerization. Software was used to calculate the electron density distribution of the push-pull, intramolecular charge transfer (ICT) operating in donor-π-conjugation-acceptor (D-π-A) configurations of dye monomer 3. It can be constructed an acid/base-induced molecular switch by modulation of intramolecular charge transfer with protonation/deprotonation. The lower critical solution temperature (LCST) behavior was investigated by means of UV-vis spectroscopy that allows the measurement of the phase transition from 25 to 40 °C in aqueous solution. The poly(NIPAM-co-dye) copolymer also exhibited color change when used an acid/base-induced molecular switch via control of intramolecular charge transfer (ICT). The morphology of the internal microstructure of the poly(NIPAM-co-dye) hydrogel was observed by scanning electron microscopy (SEM). The reversible switch could be obtained by thermal and acid/base stimuli. 相似文献
Segmented polymer networks containing poly(methyl vinyl ether) (PMVE) segments were prepared by free‐radical‐initiated copolymerization of PMVE‐α,ω‐dimethacrylate with styrene or 2‐hydroxyethyl methacrylate (HEMA). These networks were evaluated as thermo‐responsive solid‐phase extraction materials. Suspension‐derived polymer networks consisting of 80% of PMVE and 20% of HEMA adsorb toluene from an aqueous solution at 40°C and release the adsorbed toluene quantitatively at 20°C. 相似文献
Pseudopolyrotaxanes 4a and 5a are synthesized by two paths: a) directly from the pseudorotaxane, and b) by complexing with cucurbituril (CB[6]) in water at room temperature after the polymerization. Free radical copolymerization with CB[6] (un)complexed monomer and N‐isopropylacrylamide (NIPAAM) is carried out using a redox initiator in aqueous media at room temperature. The properties of pesudorotaxanes ( 4a and 5a ) and polymers ( 4 and 5 ) are investigated by TGA, DSC, and turbidity measurements. The lower critical solution temperatures of the NIPAAM‐containing copolymers and CB[6] are significantly higher than those of pure NIPAAM copolymers. The pseudopolyrotaxanes 4a and 5a have a higher thermal stability, as a result of threading of the CB[6] rings onto the polymer side groups.
