No abstract

Four series of poly(N-isopropylacrylamide) (PNIPAM) (core)/poly(N-isopropylacrylamide-co-3-acrylamidophenylboronic acid) (P(NIPAM-AAPBA)) (shell) microgels were synthesized by the modification of PNIPAM (core)/poly(N-isopropylacrylamide-co-acrylic acid) (P(NIPAM-AA)) (shell) microgels with 3-aminophenylboronic acid (APBA). Their thermosensitive behaviors were studied by dynamic light scattering. Two or three phase transitions were detected depending on the shell thickness. These transitions were confirmed by the first derivative plot of the turbidity data. The first transition occurring at about 17 degrees C was assigned to that of the P(NIPAM-AAPBA) shell, whereas the second and third ones, which occur at about 22 and 28 degrees C, respectively, were assigned to that of the PNIPAM core. These results indicate that the influences of a shrunk P(NIPAM-AAPBA) shell on the different parts of the PNIPAM core are different. As the outer part, or the "shell" part of the PNIPAM core, directly connects with the P(NIPAM-AAPBA) shell, its phase transition temperature is reduced to a larger degree as compared with that of the inner part, or the "core" part. Glucose-induced swelling was observed for all the microgels, indicating their glucose-sensitivity. However, the degree of glucose-induced swelling is much smaller than that of the pure P(NIPAM-AAPBA) microgels.

A series of lead-sensitive poly(N-isopropylacrylamide) microgels with pendant crown ether groups were prepared. Their cation-sensitive behaviors were studied by dynamic light scattering. When ionic strength is not controlled, adding salts causes the microgel particles to deswell. However, when the salt effect is ruled out by keeping a constant ionic strength, adding Pb 2þ results in much larger swelling. The Pb 2þ -induced swelling was explained by the formation of hostguest complex between Pb 2þ and the pendant crown ether groups, which increases the hydrophilicity of the polymer and accordingly the degree of swelling. The lead sensitivity of the microgels increases with increasing crown ether content. For the modified microgel with the highest crown ether content, it swells to $430% of its original volume at [Pb 2þ ] ¼ 10 mM. Other cations also increase the swelling degree of the modified microgels. The extent of the cation-induced swelling mainly depends on their affinity to the pendant crown ether groups. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4120-4127, 2010

2015): Synthesis and characterization of a novel drug-loaded polymer, poly(lactic acid-co-aminomethyl benzimidazole), Designed Monomers and Polymers, Using aminomethyl benzimidazole (AMB) as a model of benzimidazole-type drugs, a potential biodegradable drug-loaded polymer poly(lactic acid-co-aminomethyl benzimidazole) (PLAAMB) is synthesized as designed via direct melt polycondensation starting from D,L-lactic acid (LA). When the molar feed ratio LA/AMB is 40/1, the optimal synthetic conditions, including catalyst type and dosage, polycondensation temperature, and copolymerization time are discussed. After the prepolymerization at 140°C for 8 h, using 0.4 wt% stannous oxide (SnO) as the catalyst, the melt copolymerization at 160°C for 6 h gives the copolymer with the biggest weight-average molecular weight (M w ) 5300 Da. The structure and properties of the copolymer are systematically characterized with Fourier transform infrared, 1 H NMR, gel permeation chromatography, differential scanning calorimetry, and X-ray diffraction. And the investigations on the influences of different molar feed ratios on the properties of PLAAMB show that, the copolymer PLAAMB with the biggest M w of 9400 Da can be obtained. After the drug model AMB as a monomer is introduced into polylactic acid during the condensation, the T g of the obtained PLAAMB is lower than the T g of homopolymer poly(D,L-lactic acid) (PDLLA). The M w and crystallinity of PLAAMBs can meet the requirement of drug-loaded polymers in the drug delivery.