“Schizophrenic” Self-Assembly of Block Copolymers Synthesized via Aqueous RAFT Polymerization: From Micelles to Vesicles†Paper number 143 in a series on Water-Soluble Polymers.

Abstract

Dually responsive poly[(N,N-diethylaminoethyl methacrylate)-b-(N-isopropyl acrylamide)]s (P(DEAEMA-b-NIPAM)s) capable of "schizophrenic" aggregation in aqueous solution were synthesized via aqueous reversible addition-fragmentation chain transfer (RAFT) polymerization. The nanoassembly morphologies, dictated by the hydrophilic mass fraction, can be controlled by the polymer block lengths, solution pH, and temperature. Both P(DEAEMA 98 -b-NIPAM 209 ) (52.5 wt % NIPAM) and P(DEAEMA 98b-NIPAM 392 ) (70.8 wt % NIPAM) self-assemble into PDEAEMA-core PNIPAM-shell spherical micelles with a hydrodynamic radii (R h ) of 21 and 25 nm, respectively, at temperatures below the lower critical solution temperature of PNIPAM and at solution pH values greater than the pK a of PDEAEMA. The two block copolymers, however, display quite different temperature-responsive behaviors at pH < 7.5. At elevated temperatures (>42 °C) P(DEAEMA 98 -b-NIPAM 209 ) forms spherical micelles (R h =28 nm) with hydrophobic PNIPAM cores stabilized by a hydrophilic PDEAEMA shell. By contrast, P(DEAEMA 98 -b-NIPAM 392 ) assembles into vesicles (R h =99 nm) above 38 °C. The nanostructures were characterized by a combination of dynamic and static light scattering as well as transmission electron microscopy and are being investigated for their potential application as drug delivery vehicles. † Paper number 143 in a series on Water-Soluble Polymers.

pH-Responsive non-ionic diblock copolymers: protonation of a morpholine end-group induces an order–order transition

“…[49][50][51] S spherical micelles and vesicles, which are capable of forming two (or even three) self-assembled nano-structures in aqueous solution as a function of pH. [52][53][54][55][56] The effects of polymer end-groups have been studied by the examination of temperature and pH as external triggers. For example, the aqueous solution behaviour of both a poly(2-hydroxyethyl methacrylate) homopolymer prepared with a Nmorpholine ATRP initiator 57 and a series of carboxylic acid terminated poly(N-isopropylacrylamide) (PNIPAM) oligomers 58 were each shown to depend on solution pH.…”

Living Radical Polymerization by the RAFT Process – A Third Update

“…DMAm [348] DMAm-b-HEAm [348] 97 n ϭ 1 or 2 [349,350] DEAEMA [351] DMAEMA [350,352] PEGMA [224,[353][354][355] (412) [243] PAA [356] DMAm [326] DMAm [326] HPMAm [357] 357 [357] MAA/PEGMA [354] APMAm/DEAPMAm [358] APMAm/DMAPMAm [358] DEAEMA-bNIPAm [351] DMEAEMA-b-NIPAm [359] PEGMA/MAA-b-St [354,360] PEGMA/MAA-bBzMA [361] PEGMA/MAA-b-327 [362] PAA-bDMAm/408 [356] DMAEMA-b-(PAA/BMA/ DMAEMA) [350,352] HPMAm/450/451 [363] HPMAm-b-357 [357] 98 [364] 317 [311] 332 [365] 333 [365] DMAm [366] BA [366] 350 [311] NIPAm [366,367] MAA/ MMA [368] MAA/DFHA [369] OeMA/MMA [364] 332-b-MMA [365] 333-b-MMA [365] NIPAm-bDMAEAm [367] 99…”

Micellization and gelatinization in aqueous media of pH- and thermo-responsive amphiphilic ABC (PMMA82-b-PDMAEMA150-b-PNIPAM65) triblock copolymer synthesized by consecutive RAFT polymerization

“…44 The FT-IR spectrum (B) of the PMMA-b-PDMAEMA contain the characteristic band for C-N stretching of DMAEMA at 1020 cm S2 †). 45,48,49 From structure signals, we calculated the ratio of the integral peak area between the methylic protons of PMMA (marked c) and the para-C 6 H 5 protons of CPADB (marked 1), the Dp of PMMA was estimated to be about 82. Similarly, the Dp of other polymers could be also roughly calculated.…”