Morphology Control of Highly Sulfonated Block Copolymers by a Simple Thermal Process

Abstract

Well‐defined sulfonated block copolymers were prepared by direct thermolysis with block copolymers of n‐butyl acrylate (nBA) and neopentyl styrene sulfonated (NSS), which were synthesized by Cu‐based living radical polymerization ($\overline M _{\rm w} /\overline M _{\rm n}$ <1.20). A simple thermal process for 10 min at 150 °C completely deprotected the neopentyl groups in the poly(NSS) block segment to give fully sulfonated polystyrene backbone. SAXS profile of the block copolymer with 47 wt.‐% of poly(NSS) showed lamella structure, which appeared more clearly with long ranged order after sulfonation of the block copolymer.magnified image

Controlled synthesis of poly(neopentyl p‐styrene sulfonate) via reversible addition‐fragmentation chain transfer polymerisation

“…TGA shows a mass loss of 10.9% for the block copolymer during thermal treatment at 150 °C, which is attributed to loss of the neopentyl protecting group. The theoretical mass loss for complete removal of the neopentyl group in our block copolymer is 12.6% and the discrepancy observed herein is attributed to a Friedel − Crafts side reaction, where an extremely small portion of the neopentyl groups are attacked by (and thus attach to) the aromatic rings on the sulfonate repeat units, as reported in the literature . As further proof of the success of the deprotection step, FTIR spectroscopy (Fig.…”

“…Finally, to demonstrate the utility and versatility of our approach, whilst simultaneously confirming the presence of the azide moiety on the end of our polymer chains, PNSS‐N 3 has been clicked to bisalkyne‐functionalised polybutadiene, PBD‐dialkyne, to produce a hydrophobic block copolymer, PNSS‐ b ‐PBD‐ b ‐PNSS. Upon thermolysis, this block copolymer becomes amphiphilic as the PNSS block is deprotected to generate PSS end blocks, as previously shown for PNSS‐ b ‐poly( n ‐butyl acrylate) . The use of azide‐alkyne click chemistry herein opens up this approach to a whole host of hydrophobic polymers, not just those capable of being polymerised by radical chemistries.…”

“…To circumvent this problem, Okamura et al reported a novel approach to producing amphiphilic PSS‐containing copolymers by synthesising a sulfonate ester precursor, neopentyl p ‐styrene sulfonate (NSS), and converting it into its sulfonic derivative, either chemically or by thermal treatment, post polymerisation. This strategy was subsequently adopted by several groups to produce PSS‐containing copolymers using different types of controlled radical polymerisation techniques, NMP, ATRP and RAFT, for a wide range of applications. Given that this approach allows the use of common organic solvents during polymer synthesis, the material can be easily combined with other hydrophobic components, subsequently processed into thin films and finally deprotected to restore the hydrophilic, ionic character of the sulfonic acid group.…”

100th Anniversary of Macromolecular Science Viewpoint: Block Copolymers with Tethered Acid Groups: Challenges and Opportunities

“…Recent advances in the controlled polymerization of polar monomers are promising for acid-tethered polymers. These advances enable the diversification of the types of polymer backbones and use of tailor-made monomers, as summarized in Figure e–h. ,,,,− ,− This results in faster polymer chain relaxation with lowering T g , and increasing dielectric constant of the polymer backbones . The mechanical integrity of the resultant polymers is tenable via the insertion of cross-linkable moieties. , This is all aimed at simultaneously enhancing the conductivity and mechanical stability over a wider temperature range; however, the required breakthrough has not occurred yet.…”

“…The current research progress in acid-tethered polymers is closely related to the controlled synthesis of high-precision polymers with tailor-made monomers. − To date, various types of acid moieties have been added to several polymers with tunable glass transition temperatures ( T g ) − and polarities. − This has enabled the high-yield preparation of proton-conducting polymers with linear diblock, ,,− triblock, , pentablock, , and comb shapes . Therefore, the exploration of the structure–transport relationship became possible.…”