No abstract

A well-defi ned (BA)(AC) 2 miktoarm star diblock copolymer, (PPEGMA 32 -b -PMMA 41 )-b -(PMMA 45 -b -PNIPAm 19 ) 2 , is synthesized by the combination of ATRP and click reaction. The miktoarm star block copolymer and its precursors are characterized by means of NMR and SEC/MALLS measurements. The copolymer exhibits a low critical aggregation concentration in aqueous solution. Micelles that self-assemble from the copolymer are prepared in aqueous solution below 15 °C by a sonication method. The micelles have a PMMA core and a PPEGMA/PNIPAm corona and exhibit temperature sensitivity. Using celecoxib as a guest molecule, it is found that the loading capacity of the star copolymer is 8.8 wt% and the celecoxib release from the loaded self-assembly is temperature tunable.

Poly(N‐isopropylacrylamide) (PNIPAm) core cross‐linked star (CCS) polymers (s‐(PNIPAm)n) are synthesized by arm‐first ATRP method. The related synthesis conditions are investigated and optimized. By varying cross‐linker N,N‐methylenebisacrylamide (BIS) concentration, PNIPAm CCS polymers with about 47, 86, and 211 arms are synthesized. Then, under ATRP condition, the “living” sites at the core of s‐(PNIPAm)n reacting with a monovinyl β‐cyclodextrin (β‐CD) monomer afford β‐CD functionalized s‐(PNIPAm)n (CDF‐SPNIPAm). The structures of the star polymers are characterized. The results indicate that in CDF‐SPNIPAm, the ratio of β‐CD units to PNIPAm arm numbers could be up to 0.6:1. The fluorescence spectra of star polymer/ANS (8‐­anilino‐1‐naphthalenesulfonic acid ammonium salt hydrate) systems prove that the β‐CD moieties of CDF‐SPNIPAm are available for including guest molecules. By using pH‐sensitive adamantyl (Ada)‐terminated poly(4‐vinylpyridine) (Ada‐P4VP) (synthesized by ATRP strategy) as a model guest macromolecule, the host–guest complexation between β‐CD units of CDF‐SPNIPAm and adamantyl groups of Ada‐P4VP is confirmed via 2D NOESY 1H NMR and DLS measurements. The results indicate that the presence of the Ada‐P4VP arms provides temperature‐responsive star polymers with pH sensitivity. Therefore, the β‐CD‐functionalized star PNIPAm could provide host macromolecular platform for constructing novel miktoarm star polymers.