Glass transition and molecular dynamics in PHPMA-b-POEGMA block copolymers

Molecular dynamics and crystallization in polymers based on ethylene glycol methacrylates (EGMAs) with melt memory characteristics: from linear oligomers to comb-like polymers

“…In Fig. S6 in the ESI, † we demonstrate the vanishing of b of POEGMA-long (under ambient conditions) upon drying (at B2 rh% over P 2 O 5 ), while, in our recent study 35 on the same POEGMA-short however purposely dried therein, b was also absent. Therefore, we conclude that b relaxation here arises from the hydrophilic part of our amphiphilic OEGMA chains, and is triggered by the presence of water molecules.…”

“…Four samples are studied here, shown schematically in Scheme 1, namely two commercial linear OEGMAs (Sigma-Aldrich) with short (475 g mol À1 , d p = 8-9, B4 nm, OEGMA-short) 35 and long (950 g mol À1 , d p = 19 B8 nm, OEGMA-long) chains and two comblike polymers, POEGMA-short and POEGMA-long, consisting of 10 branches on average, that are the linear OEGMA-short and OEGMA-long, respectively. The POEGMAs were synthesized using the abovementioned short and long oligomers via the reversible addition-fragmentation chain transfer (RAFT) polymerization process (Scheme 2).…”

“…In order to prepare POEGMA polymers with short 35 and long side chains, reversible addition fragmentation chain transfer polymerization (RAFT polymerization) was employed, using 4-cyano-4-(phenylcarbonothioylthio)pentanoic acid (CPAD) as the chain transfer agent (CTA), 2,2-azobis(isobutyronitrile) (AIBN) as the radical source, to a CTA to initiator ratio ([CTA] 0 /[I] o ) of 5 : 1 and 1,4-dioxane as the polymerization solvent. Before the polymerization reaction, the OEGMA monomers (M n = 475 g mol À1 and M n = 950 g mol À1 ) were purified using a filled column including inhibitor removers (butylated hydroxytoluene and hydroquinone monomethyl ether, obtained from Sigma-Aldrich).…”

“…Considering the probable molecular origins for these dynamics as described above we can rationalize this effect via the concept of less inter-molecular interactions in the OEGMAs and, on the other hand, of more geometrical constraints in the mobility of side chains in the comb-like POEGMAs. Consequently, we expect the g and b processes to be activated, on the one hand, from the same molecular groups, 35 however, in the comb-like entities of POEGMA under more 'constraints'.…”