End‐group controlling aqueous solution properties in star‐shaped poly(2‐hydroxyethyl acrylate) and poly(2‐hydroxyethyl acrylate)‐b‐poly(N‐isopropylacrylamide) polymers

Abstract

Star‐shaped poly(2‐hydroxyethyl acrylate) (PHEA)6 polymers were synthesized using hexafunctional chain transfer agent (CTA) trithiocarbonate type via reversible addition‐fragmentation chain transfer (RAFT) polymerization. The (PHEA)6 polymers with dodecyl chain‐end were non‐water soluble. As the molecular weight increased, the polymers could disperse in water, forming large aggregates with a DH of 1027 to 525 nm. On the contrary, the (PHEA)6 polymers with the carboxylic acid group at the chain‐end were completely soluble in water. Then, (PHEA)6 polymers were chain extended with N‐isopropylacrylamide (NIPAM) to obtain poly(2‐hydroxyethyl acrylate)‐b‐poly(N‐isopropylacrylamide) (PHEA‐b‐PNIPAM) block copolymers. The dodecyl group strongly affects the aqueous solution properties of the copolymers even with a high PNIPAM content. Copolymers with dodecyl chain‐end were insoluble or partially soluble in water, forming large aggregates (0.5 mg/ml in distilled water). The copolymers with carboxylic acid end‐group were totally water soluble. The thermo‐responsive phase behavior of the star‐shaped block copolymers was studied, and for this purpose, it was necessary to remove the RAFT group containing the dodecyl tail. The intense turbidity observed in the aqueous dispersions of the corresponding copolymers made it challenging to determine the LCST accurately. The copolymers with a carboxylic end group were evaluated as is.

Self-assembled PHEA-based block copolymers for the synthesis of gold nanoparticles

“…Star six-arm poly(2-hydroxyethyl acrylate) polymers were synthesized as described in our previous work. 17 Fig. S1 (ESI†) shows the 1 H NMR spectra for the (PHEA) 6 homopolymer used as the starting material.…”

“…Poly(2-hydroxyethyl acrylate) polymers were synthesized as described in our previous work. 17 All samples were acetylated for analysis ( 1 H NMR and GPC).…”

“…1,2 There are many examples of polymers frequently used as templates: poly(acrylic acid) (PAA), 15 poly(glycidyl acrylate) (PGA), 16 and poly(2-hydroxyethyl acrylate) (PHEA). 17 Poly(2-hydroxyethyl acrylate) (PHEA) is an excellent template for side chain modification due to its primary hydroxyl groups that can be functionalized by an esterification reaction. 17 PHEA has also been partially or fully functionalized with phthalic anhydride, 17 acetic anhydride, 17,18 and folic acid.…”

“…17 Poly(2-hydroxyethyl acrylate) (PHEA) is an excellent template for side chain modification due to its primary hydroxyl groups that can be functionalized by an esterification reaction. 17 PHEA has also been partially or fully functionalized with phthalic anhydride, 17 acetic anhydride, 17,18 and folic acid. 19 PHEA is a hydrophilic, nontoxic, and non-ionic polymer.…”