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Many common polymers, especially vinyl polymers, are inherently difficult to chemically recycle and are environmentally persistent. The introduction of low levels of cleavable comonomer additives into existing vinyl polymerization processes could facilitate the production of chemically deconstructable and recyclable variants with otherwise equivalent properties. Here, we report thionolactones that serve as cleavable comonomer additives for the chemical deconstruction and recycling of vinyl polymers prepared through free radical polymerization, using polystyrene (PS) as a model example. Deconstructable PS of different molar masses (∼20-300 kDa) bearing varied amounts of statistically incorporated thioester backbone linkages (2.5-55 mol %) can be selectively depolymerized to yield well-defined thiol-terminated fragments (10 kDa) that are suitable for oxidative repolymerization to generate recycled PS of nearly identical molar mass to the parent material, in good yields (80-95%). A theoretical model is provided to generalize this molar mass memory effect. Notably, the thermomechanical properties of deconstructable PS bearing 2.5 mol % of cleavable linkages and its recycled product are similar to those of virgin PS. The additives were also shown to be effective for deconstruction of a cross-linked styrenic copolymer and deconstruction and repolymerization of a polyacrylate, suggesting that cleavable comonomers may offer a general approach toward circularity of many vinyl (co)polymers.

Metal-free hydrosilylation using tris(pentafluorophenyl)borane (B(C6F5)3) as a catalyst enables the rapid polymerization of α-diketone and bis(silane) monomers under ambient conditions to give high molecular weight poly(silyl ether)s (PSEs). A wide selection of commercially available monomers bearing different backbone and side-chain functional groups are shown to be compatible with these metal-free conditions. Significantly, the thermal properties of these poly(silyl ether)s are highly tunable, with novel semicrystalline materials being obtained in a variety of cases. These poly(silyl ether) materials serve as a versatile platform for materials with designed degradation profiles and crystallinity.

Combination chemotherapy must strike a difficult balance between safety and efficacy. Current regimens suffer from poor therapeutic impact because drugs are given at their maximum tolerated dose (MTD), which compounds the toxicity risk and exposes tumors to non-optimal drug ratios. A modular framework has been developed that selectively delivers drug combinations at synergistic ratios via tumor-targeting aptamers for effective low-dose treatment. A nucleolin-recognizing aptamer was coupled to peptide scaffolds laden with precise ratios of doxorubicin (DOX) and camptothecin (CPT). This construct had an extremely low IC50 (31.9 nm) against MDA-MB-231 breast cancer cells in vitro, and exhibited in vivo efficacy at micro-dose injections (500 and 350 μg kg-1 dose-1 of DOX and CPT, respectively) that are 20-30-fold lower than their previously-reported MTDs. This approach represents a generalizable strategy for the safe and consistent delivery of combination drugs in oncology.

Vulcanization of silicone networks from commercially available linear poly(dimethyl-co-methylhydro)siloxane (PMHS) and alpha-diketones was achieved using metal-free borane hydrosilylation at room temperature. The Lewis acid catalyst, tris(pentafluorophenyl)borane (B(C6F5)(3)), efficiently cross-linked PMHS at minimal catalyst loadings (200-1000 ppm) to produce polymer networks with mechanical properties, thermal stability, and optical clarity rivaling that achieved from traditional platinum catalysis. Variation of the starting PMHS structure is shown to influence the final characteristics of the network. Increasing molar mass of the PMHS chain results in a higher thermal decomposition temperature, while increasing mole fractions of Si-H moieties along the backbone increase the cross-linking density and the attendant Shore hardness. The degradation behavior of the networks was investigated, with the borane-vulcanized samples showing rapid dissolution upon exposure to acid and high stability to neutral and basic conditions. Functional networks bearing halide and vinyl groups could also be prepared via a preliminary reaction of PMHS with an appropriate monoketone, providing a general and versatile strategy for network derivatization with the potential for postvulcanization functionalization being subsequently demonstrated via thiol-ene click chemistry.