Real-Time and in Situ Investigation of “Living”/Controlled Photopolymerization in the Presence of a Trithiocarbonate

Polymerization of methyl acrylate under ultraviolet (UV) irradiation in the presence of <i>S</i>-1-dodecyl-<i>S</i>′-(α,α′-dimethyl-α″-acetic acid) trithiocarbonate (DDMAT) was investigated by in situ ¹H nuclear magnetic resonance spectroscopy. Effects of light intensity, wavelength, and concentration of DDMAT on the polymerization behaviors were studied in detail. The experimental results demonstrate that the “living” features of the photopolymerization are related to the concentration of DDMAT. “Living”/controlled radical polymerization was successfully achieved with a high concentration of DDMAT. However, with a low concentration of DDMAT, the polymerization proceeded in an uncontrolled manner and produced polymers with high molecular weights and broad polydispersities. Photochemical behavior of DDMAT was studied in detail, and the results showed that the photolysis of DDMAT was reversible at high concentration, whereas contrarily, DDMAT decomposed irreversibly at low concentration. A possible mechanism was proposed for the reversible photolysis of DDMAT at high concentration, which may involve both reversible termination and reversible addition–fragmentation chain transfer approaches

Synthesis and Luminescence of POSS-Containing Perylene Bisimide-Bridged Amphiphilic Polymers

A novel well-defined amphiphilic fluorescent polymer containing asymmetric perylene bisimide was designed and synthesized by combining reaction of perylene anhydride with amino functional polyhedral oligomeric silsesquioxane (POSS) and atom transfer radical polymerization (ATRP) of <i>N</i>-isopropylacrylamide (NIPAM). All the intermediate and final products were characterized by NMR, Fourier transform infrared spectroscopy (FT-IR), elemental analyses, and gel permeation chromatograph (GPC). Self-assembly of the amphiphilic polymers was investigated in aqueous solution and POSS-containing hybrid nanoparticles were obtained and characterized by dynamic laser light scattering (DLS) and transmission electron microscopy (TEM). The novel hybrid nanoparticles exhibit attractive high red fluorescence at 645 nm due to the significant effect of the bulky POSS moieties. Moreover, based on the thermoresponsive PNIPAM coronas, the fluorescence intensity of the self-assembled hybrid nanoparticles can be further enhanced and tuned by changing temperature

Sustainable Electrospun Poly(l‑lactic acid) Fibers for Controlled Release of the Mosquito-Repellent Ethyl Butylacetylaminopropionate (IR3535)

Fibers composed of poly(l-lactic acid) (PLLA) and the mosquito-repellent ethyl butylacetylaminopropionate (IR3535) were prepared by solution electrospinning. Defect-free and uniform monoaxial fibers with a diameter of the order of magnitude of 1 μm were obtained. Thermogravimetric analyses showed that it is possible to incorporate more than 40 m% of IR3535 into the PLLA fibers. Thermal and structural characterization indicated that IR3535 facilitates the crystallization of PLLA and formation of orthorhombic α-crystals during electrospinning. IR3535 has a plasticizing effect on PLLA, as detected by the decrease in the glass transition temperature. The release of IR3535 from PLLA/IR3535 fibers to the environment was quantified by thermogravimetric analysis at different temperatures ranging from 60 to 100 °C, suggesting rather slow evaporation of the repellent, with a time constant of few days at body temperature. The observed results indicate a possible use of electrospun PLLA/IR3535 fiber mats as part of a long-lasting repellent-delivery system and application in the field of combating diseases caused by mosquito bites

Catalyst-Free, Mechanically Robust, and Ion-Conductive Vitrimers for Self-Healing Ionogel Electrolytes

Vitrimers have been widely employed in self-healing, recyclable, and shape-shifting materials. However, the application of catalyst-free vitrimers to create self-healable and mechanically robust gel polymer electrolytes (GPEs) remains a challenge, often limiting the potential of vitrimer-based materials. Herein, we utilized a catalyst-free dynamic covalent bond (silyl ether) as a linkage to prepare self-healable and mechanically robust GPEs, which are fully reprocessable. By incorporating polymeric ionic liquids into the dynamically cross-linked networks, both ion conductivity and mechanical properties can be flexibly tuned. The dynamic property of the network was demonstrated through frequency sweep rheology, which revealed a rubbery-like behavior at high frequencies and a liquidlike behavior at low frequencies. This dynamic feature enables self-healing and allows for reprocessing via embedding of such dynamic covalent networks into the GPEs. The GPEs containing 80 wt % of a bis(trifluoro­methansulfonamide) lithium/ionic liquid (LiTFSI/IL) mixture exhibited good ion conductivites of 0.13 mS/cm at 20 °C and 1.88 mS/cm at 80 °C. Furthermore, the elastic modulus of the GPEs could reach a value of 0.24 MPa and was able to persist through electrode-volume expansions during charging/discharging.The tunable dynamic properties, coupled with high ion conductivity and a high modulus, indicate promising applications for this type of dynamic bond in sustainable solid electrolytes