Effects of Substitution Groups on the RAFT Polymerization of N-Alkylacrylamides in the Preparation of Thermosensitive Block Copolymers

Abstract

Reversible addition−fragmentation chain transfer (RAFT) polymerization was used to prepare a series of homo- and copolymers of N-alkyl-substituted acrylamides. The acrylamide monomers have similar chemical structures, but they all exhibit difference in reactivities, especially between N-monosubstituted and N,N-disubstituted acrylamides during the RAFT process. Results from size exclusion chromatography and matrix-assisted laser desorption ionization time-of-flight mass spectrometry indicate chain transfers to monomers are easier to occur for N-monosubstituted polyacrylamides, with negative deviations of the molecular weights from the theoretical values. The high transfer activity makes them good macro-chain transfer agents (CTAs). The stronger electron-donating conjugative effect renders the disubstituted acrylamides more reactive, meaning that they can react more readily with monosubstituted polyacrylamide−CTAs to form a sequent block. Tri- and tetrablock copolymers with multiple thermosensitivity have been successfully prepared and tested following these guiding principles.

Living Radical Polymerization by the RAFT Process - A Second Update

“…MMA [296] St [296] 128* [283] S S C 12 H 25 S CO 2 H AA [91] CA [297] tBA [298] MA [299] (BMA) [300] (BMA) [300] CMA [301] MMA [122,283] (MMA) [122] BAM [302] DEAM [302,303] DMAM [302,303] EMAM [302,303] NIPAM [302][303][304][305][306] PAM [302,306] MVK [307] PVK [307] 297 [308] tBS [276] CMS [309] HMS [309] St [91,300,309] (St) [300] 4VP [310] Ip [311] 320 [312] 325 [100] 327 [309] 331 [313] 332 [313] NVP [103] 331-b-St [313] tBA-b-Ip [298] tBA-b-St [298] tBA-b-IP-b-St …”

“…[302] Bivigou-Koumba et al [286] reported that strong retardation was observed in extending PSt macro-RAFT agents with N-isopropylacrylamide (NIPAM), whereas chain extension of PNIPAM macro-RAFT with St was successful. In both cases slow initiation by the macro-RAFT agent-derived propagating species was suggested as a possible explanation.…”

Assembly behavior of double thermo-responsive block copolymers with controlled response temperature in aqueous solution

“…In addition, compelling studies have been conducted to examine the effects of changing the LCST, using block-or graftcopolymerization [23,24], immobilization [25], and terminal [26,27], and altering other factors. Recently, multiple thermo-responsive block polymers have been synthesized that include a polyNIPAAm block [28]. For example, polyNIPAAm-bpoly(3-[N-(3-methacrylamidopropyl)-N,N-dimethyl]ammoniopropane sulfonate) was synthesized with a double thermo-response using two blocks that possessed both LCST and UCST.…”

Stimuli Responsive Carriers: Magnetically, Thermally and pH Assisted Drug Delivery

“…Some example of these categories are Poly( N -vinylcaprolactam) [ 34 ], Poly( N -isopropylacrylamide) [ 35 ], Poly( N , N -ethylmethylacrylamide) [ 36 ], Poly( Nethylacrylamide ) [ 37 ], Poly( N , N -diethylacrylamide) [ 38 ]. A typical UCST system is based on a combination of acrylamide and acrylic acid [ 6 ].…”