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The theory of kinetics of the swelling of a gel previously developed by Tanaka and Fillmore has been generalized to include the effect of nonnegligible shear modulus. The values of the cooperative diffusion coefficient and of the ratio of the shear modulus over the longitudinal osmotic modulus obtained from macroscopic swelling experiments in polyacrylamide gels show good agreement with previous results.

The gel relaxation times of two different poly­[styrene-b-(ethylene-alt-propylene)-b-styrene] (SEPS) ABA triblock copolymers in squalane at various concentrations has been measured by rheology. These relaxation times were compared with the results of previous time-resolved small-angle neutron scattering (TR-SANS) experiments, which measured chain exchange kinetics in SEP diblock and SEPS triblock micelles in squalane. The gels relaxed up to four orders of magnitude faster than expected based on the chain exchange measurements of equivalent diblock polymers. By accounting for two factorsa bias toward shorter end-block lengths in the gel relaxation, and a reduction in the energy barrier to chain pullout caused by the triblock architecturea model is constructed that reconciles the surprisingly short gel relaxation times with the chain exchange times measured via TR-SANS.

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As the complexity of polymer structure grows, so do the challenges for developing an accurate understanding of their structure–property relationships. Here, the synthesis of bottlebrush polymers with topologically precise and fully discrete structures is reported. A key feature of the strategy is the synthesis of discrete macromonomer libraries for their polymerization into topologically precise bottlebrushes that can be separated into discrete bottlebrushes ( Đ = 1.0). As the system becomes more discrete, packing efficiency increases, distinct three-phase Langmuir−Blodgett isotherms are observed, and its glass transition temperature becomes responsive to side-chain sequence. Overall, this work presents a versatile strategy to access a range of precision bottlebrush polymers and unravels the impact of side-chain topology on their macroscopic properties. Precise control over side chains opens a pathway for tailoring polymer properties without changing their chemical makeup.