Influence of <scp>pH</scp> on the Self‐Assembly Properties of Heterofunctional <scp>POEGMA</scp>‐Based Block Copolymers During <scp>RAFT</scp>‐<scp>PISA</scp>

ABSTRACT POEGMA‐based block copolymers self‐assemblies with surface‐functionalized carboxylic acid or propargyl groups were synthesized by successive reversible addition‐fragmentation chain transfer (RAFT) polymerization of oligo(ethylene glycol) methyl ether methacrylate (OEGMA) and RAFT‐mediated polymerization‐induced self‐assembly (RAFT‐PISA) in dispersion of 2‐(methacryloyloxy)‐ N,N,N ‐trimethylethanaminium hexafluorophosphate (METAPF 6 ). The temperature responsive properties of the carboxylic acid–terminated POEGMA (POEGMA CDP ) and propargyl‐terminated POEGMA (POEGMA CDPy ) were studied in aqueous buffer solutions at pH 2.3 and 9.2. At pH 2.3, POEGMA CDP aqueous solution exhibits a cloud point while no cloud point was observed at pH 9.2. POEGMA CDPy shows a cloud point at both pH levels. The RAFT‐PISA in dispersion of METAPF 6 at 75°C in either pH 2.3 or 9.2 buffer solution using POEGMA CDP or POEGMA CDPy as macro‐RAFT agents led to block copolymers, as confirmed by DOSY analysis. For POEGMA CDP (DP n = 9), DP n ,NMR,PMETAPF6 was 47 at pH 2.3 and 27 at pH 9.2 and for POEGMA CDPy (DP n = 10), DP n ,NMR,PMETAPF6 was 36 at pH 2.3 and 22 at pH 9.2, as shown by 1 H NMR spectroscopy. Both in situ POEGMA CDP ‐ b ‐PMETAPF 6 and POEGMA CDPy ‐ b ‐PMETAPF 6 self‐assemblies in aqueous solutions exhibited an increase in D h and PDI when the pH increased from 2.3 to 9.2, as measured by DLS at 20°C. TEM analyses revealed almost spherical self‐assemblies, unaffected by pH or chain‐end functionality.