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Previous studies have demonstrated that films of sequence‐controlled amphiphilic copolymers display contact angles that depend on microblock size. This suggests that microblock length may provide a means of tuning surface and interfacial properties. In this work, the interfacial rheology of a series of sequence‐controlled copolymers, prepared through the addition of bicyclo[4.2.0]oct‐1(8)‐ene‐8‐carboxamide (monomer A) and cyclohexene (monomer B) to generate sequences up to 24 monomeric units composed of (AmBn)i microblocks, where m, n, and i range from 1 to 6. Interfacial rheometry is used to measure the mechanical properties of an air–water interface with these copolymers. As the microblock size increases, the interfacial storage modulus, G′, increases, which may be due to an increase in the size of interfacial hydrophobic domains. Small‐angle X‐ray scattering shows that the copolymers have a similar conformation in solution, suggesting that any variations in the mechanics of the interface are due to assembly at the interface, and not on solution association or bulk rheological properties. This is the first study demonstrating that microblock size can be used to control interfacial rheology of amphiphilic copolymers. Thus, the results provide a new strategy for controlling the dynamics of fluid interfaces through precision sequence‐controlled polymers. [ABSTRACT FROM AUTHOR]

Alginate hydrogels have shown great promise for applications in wound dressings, drug delivery, and tissue engineering. This report details the fabrication and rheological properties of a multicomponent hydrogel consisting of alginate and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers, and the achievement of thick, castable gels with tunable, thermoreversible behavior at physiological temperatures. PEO-PPO-PEO triblock copolymers can form temperature-sensitive hydrogels that exist as liquids at low temperatures and soft solids at high temperatures. In this work, we have employed PEO-PPO-PEO triblock copolymers to impart thermoresponsive properties to alginate hydrogels in the form of a multicomponent hydrogel. These systems can transition between a weak gel and a stiff gel, with a corresponding increase in the viscoelastic moduli of approximately two orders of magnitude as temperature is increased. The temperatures corresponding to the upper and lower boundaries of the stiff gel region, as well as the storage modulus at physiological temperatures (e.g., 36–40 °C), can be controlled through the PEO-PPO-PEO concentration. Optically clear gels that are homogeneous on the microscale can be fabricated in a scalable manner to create flat, large-area thick films, making these systems favorable for applications in wound healing, soft tissue repair, and biomedical device coatings. [ABSTRACT FROM AUTHOR]

• Microscale structures are observed in hydrogels of PLA-PEO-PLA block copolymers. • Nature of the microstructure depends on stereochemistry of the PLA block. • Clear micropores and mass fractal structure for gels with a higher l / d -lactide ratio. • More uniform surface fractal structure for gels with a 50/50 l / d -lactide ratio. • Stereochemistry can be used to tune microstructure of polymeric biomaterials. Understanding the development of microstructure (e.g., structures with length scales roughly 0.5–500 μm) in hydrogels is crucial for their use in several biomedical applications. We utilize ultra-small-angle neutron scattering (USANS) and confocal microscopy to explore microstructure of poly(lactide)-poly(ethylene oxide)-poly(lactide) (PLA-PEO-PLA) triblock copolymer hydrogels with varying l / d -lactide ratio. We have previously found that these polymers self-assemble on the nanoscale into micelles. Here, we observe large-scale structures with diverse morphologies, including highly porous self-similar networks with characteristic sizes spanning approximately 120 nm–200 μm. These structural features give rise to power-law scattering indicative of fractal structures in USANS. Mass fractal and surface fractal structures are found for gels with l/d ratios of 80/20 and 50/50, respectively. Confocal microscopy shows microscale water-filled channels and pores that are more clearly evident in gels with a higher fraction of l -lactide in the PLA block as compared to the 50/50 hydrogels. Tuning block stereochemistry may provide a means of controlling the self-assembly and structural evolution at both the nanoscale and microscale, impacting application of these materials in tissue engineering and drug delivery. [ABSTRACT FROM AUTHOR]

We report on the nanoscale assembly of poly(lactic acid)- b- poly(ethylene oxide)- b- poly(lactic acid) (PLA-PEO-PLA) triblock copolymers in water, focusing on the effect of stereochemistry, where the PLA blocks are statistical copolymers of l -lactide and d -lactide with l/d ratios of 100/0, 95/5, 90/10, 85/15, 75/25, and 50/50. Small-angle neutron scattering (SANS) shows a nearly constant d -spacing as concentration varies in triblock systems with l/d ratios of 90/10 and 95/5, which we attribute to inhomogeneity in the structure of these gels, supported by previous USANS and confocal microscopy studies. The SANS data fit well to a core-shell ellipsoid form factor model with a hard-sphere structure factor. Polymeric micelles with l/d ratios from 75/25 to 85/15 displayed very high aggregation numbers, consistent with a strong interaction between PLA chains and the enhanced storage modulus observed in rheological studies of these systems. While the 90/10 and 95/5 samples showed lower aggregation numbers, their SANS profiles shows close spacing between micelles, which may promote a high fraction of intermicellar bridging chains, also consistent with a higher storage modulus. Overall, these results provide insight into the micellar assembly behavior of block copolymers with a crystallizable block, and indicate that tuning stereochemistry of PLA-based block copolymers is an effective means of modifying micellar properties for specific applications. [Display omitted] • Assembly of block copolymer gels with varying block stereochemistry was explored. • SANS shows a nearly constant d -spacing with concentration for intermediate l/d ratios. • Profiles are consistent with inhomogeneity in the gel structure. • Data also suggest a high fraction of bridging chains at intermediate l/d ratios. • Results give insight into the unique rheology observed in these systems. [ABSTRACT FROM AUTHOR]