Effect of Temperature on the Mobility of Core‐Shell‐Type Nanoparticles Composed of Poly(<i>γ</i>‐benzyl‐<scp>L</scp>‐glutamate) and Poly(<i>N</i>‐isopropylacrylamide)

Abstract

Abstract Summary: Core‐shell‐type nanoparticles composed of PBLG and PNIPAAm were prepared in an attempt to study the effects of temperature on the dynamic behavior of temperature‐sensitive polymeric shell, PNIPAAm, in the nanoparticles by 1 H NMR spectroscopy. Spin‐lattice relaxation time ( T 1 ) and line halfwidth in D 2 O and CDCl 3 were measured to monitor the change of the chain mobility of PNIPAAm in the GN nanoparticles within the temperature range encompassing its LCST. The molecular motion of PBLG segment in GN nanoparticles in CDCl 3 was also examined and compared with that of the PNIPAAm. The morphology, size distribution, and effect of temperature on the sizes of the GN nanoparticles were also investigated. The temperature dependence of T 1 and line halfwidth suggests that the N ‐isopropyl group turns gradually into the solid‐like aggregates at temperatures higher than the LCST of PNIPAAm due to the collapsed coil‐globule transition. T 1 values of N ‐isopropyl groups decreased with increasing PBLG content in GN diblock copolymer, suggesting the mobility of PNIPAAm chain, as the shell, becomes more restricted at higher PBLG core content. Changes in the mobility of PNIPAAm shell in the core‐shell‐type nanoparticles composed of PBLG and PNIPAAm. magnified image Changes in the mobility of PNIPAAm shell in the core‐shell‐type nanoparticles composed of PBLG and PNIPAAm.