We report a reactive polymer platform for the rapid discovery of strongly segregated diblock polymers that microphase separate into well-defined morphologies with sub-5 nm features. Our strategy employs reactive poly­(styrene-block-2-vinyl-4,4-dimethylazlactone) (SV) polymers with low degrees of polymerization (N), in which the V blocks undergo selective and quantitative reactions with functional primary amines, to identify new poly­(acrylamides) that are highly immiscible with poly­(styrene) and induce block polymer self-assembly. Using a combination of optical birefringence and small-angle X-ray scattering (SAXS), we characterize a library of 17 block polymers produced by amine functionalization of four parent SV diblocks synthesized by sequential RAFT polymerizations. We demonstrate that V block functionalization with hydroxy- and methoxy-functional amines yields diblocks that order into lamellar mesophases with half-pitches as small as 3.8 nm. Thus, this azlactone-based reactive molecular platform enables combinatorial generation of polymer libraries with diverse side chain structures that may be rapidly screened to identify new high χ/low N systems for self-assembly at ever decreasing length scales.

We report an approach to the post-fabrication placement of chemical functionality on microphase-separated thin films of a reactive block copolymer. Our approach makes use of an azlactone-containing block copolymer that microphase separates into domains of perpendicularly-oriented lamellae. These thin films present nanoscale patterns of amine-reactive groups (reactive stripes) that serve as handles for the immobilization of primary amine-containing functionality. We demonstrate that arbitrary chemical functionality can be installed by treatment with aqueous solutions under mild conditions that do not perturb underlying microphase-separated patterns dictated by the structure of the reactive block copolymer. This post-fabrication approach provides a basis for the development of modular approaches to the design of microphase-separated block copolymer thin films and access to coatings with patterned chemical domains and surface properties that would be difficult to prepare by the self-assembly and processing of functionally complex block copolymers.

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We report the synthesis and shear rheology of a series of hydrogels derived from poly(vinyl acetate-b-vinyl alcohol-b-vinyl acetate) (PVAc-b-PVOH-b-PVAc) triblock copolymers. Bidirectional, reversible-addition−fragmentation chain transfer free radical polymerizations of vinyl acetate (VAc) and vinyl chloroacetate (VClAc) are optimized to produce a series of relatively narrow dispersity PVAc-b-P(VAcran-VClAc)-b-PVAc triblock copolymers with controlled molecular weights and compositions. Rapid and selective hydrolysis of P(VAc-ran-VClAc) blocks with K 2 CO 3 /CH 3 OH furnishes access to a series of PVAc-b-PVOH-b-PVAc amphiphiles. Hydration of solvent-cast films of these copolymers, comprising PVAc blocks of comparable degrees of polymerization with variable PVOH segment lengths, yields soft hydrogels (G′(ω) ∼ 1−10 kPa). Synchrotron small-angle and wide-angle X-ray scattering reveals that these hydrogels microphase separate into spherical hydrophobic PVAc domains that are interconnected by solvated PVOH network strands. The strain-dependent rheology of these hydrogels depends sensitively on the length of the center PVOH segment. This gel rheology is shown to stem from the hydrogen bond donor−acceptor capabilities of PVOH, which leads to the formation of weak, dynamic noncovalent crosslinks in the aqueous domains of these gels. Thus, the observed gel rheology may be rationalized in terms of the shear-induced reorganization of these H-bonding crosslinks as a function of the applied strain.

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