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This work describes the first example of a hydrogenated polybutadiene elastomer photopolymer that addresses the process constraints of vat photopolymerization (VP) additive manufacturing. A synthet...

Melt polymerization enabled the synthesis of semi-aromatic (co)polyesters containing 1,4-cyclohexanedimethanol (CHDM), 4,4′-bibenzoate (4,4′BB), and 3,4′-bibenzoate (3,4′BB). Proton nuclear magneti...

Poly(dimethyl siloxane)-containing (PDMS), segmented polyureas represent an important class of high-performance elastomers that leverage the low glass transition temperature (Tg) of PDMS and superior mechanical reinforcement from bidentate hydrogen bonding. Current synthetic methods exclusively employ highly reactive/toxic isocyanate reagents and volatile organic solvents; the latter must be quantitatively removed prior to use. This report details an isocyanate-, solvent-, and catalyst-free synthetic method towards PDMS polyureas using urea and a disiloxane diamine chain extender in the melt phase. Melt polymerization afforded segmented PDMS polyureas, which formed optically clear, mechanically ductile, freestanding films. Observation of distinct thermal transitions with differential scanning calorimetry and dynamic mechanical analysis, corresponding to the respective segments, suggested microphase separation. Tensile and hysteresis measurements corroborated similarities between these PDMS polyureas and their isocyanate-containing analogues with strain at break ranging from 495 to 1180%. This facile, isocyanate-free approach provides a commercially viable alternative to the current industrial process for high performance elastomers.

A novel, poly(dimethyl siloxane)-based photopolymer that exhibits simultaneous linear chain extension and crosslinking was suitable for vat photopolymerization additive manufacturing. Photopolymer compositions consisted of dithiol and diacrylate functional poly(dimethyl siloxane) oligomers, where simultaneous thiol-ene coupling and free radical polymerization provided for linear chain extension and crosslinking, respectively. Compositions possessed low viscosity before printing and the modulus and tensile strain at break of a photocured, higher molecular weight precursor after printing. Photorheology and soxhlet extraction demonstrated highly efficient photocuring, revealing a calculated molecular weight between crosslinks of 12,600 g/mol and gel fractions in excess of 90% while employing significantly lower molecular weight precursors (i.e.

Chemical warfare agent (CWA) sorption into polymeric coatings is an important consideration for preventing human exposure to CWAs. The specific nature of CWA–polymer interactions greatly influences the degree of gas uptake into a polymeric coating. By uncovering the role the various functional groups in CWAs play during gas sorption, better films and coatings can be engineered. This study utilized a quartz crystal microbalance to measure sulfur mustard (HD) analog (simulant) and hexane vapor uptake into polyurethane films. Analysis of the uptake data with Flory–Huggins theory yielded interaction parameter values (χ) between 0.24 and 0.40 for each HD simulant-polyurethane system compared to 0.97 for hexane, revealing the importance of the chlorine and sulfur groups in gas uptake at the thin film interface. We predict similar uptake behavior for HD in polyurethane coatings due to structural similarities between HD and the simulants.

Ultraviolet curable polyureas and polyurethanes enjoy a wide range of applications in the coatings industry. They demand less energy for curing compared to thermal processes that offer relatively low viscosities before photocuring, and provide mechanical property improvements due to hydrogen bonding physical crosslinks. Mechanical properties of the coatings are dependent on a variety of factors, including chemical composition, molecular weight, and molecular weight distribution. Formulations are designed for a wide variety of end use applications, ranging from soft, elastomeric coatings to harder, nonflexible sealants. This report demonstrates that the thermomechanical behavior of photocured coatings is a function of molecular weight distribution. Step-growth polymerization and endcapping afforded a variety of acrylate-terminated, urea-/urethane-containing photocurable oligomers from amine-terminated poly(propylene glycol), dicyclohexylmethane-4,4′-diisocyanate (HMDI), and 2-hydroxyethyl acrylate (HEA) at various stoichiometric ratios. The state-of-the-art supercritical fluid chromatography coupled with evaporative light-scattering detection (SFC-ELSD) enabled the elucidation of oligomeric molecular weight distributions as a function of reaction stoichiometry. SFC-ELSD demonstrated the efficient separation of oligomeric species with single repeat unit resolution (i.e., n = 2 vs. n = 3). Dynamic mechanical analysis probed thermomechanical response of photocured films as a function of molecular weight distribution and demonstrated that the presence of a hydrogen-bonding, small molecule photoactive reaction byproduct, i.e., HEA doubly-endcapped HMDI, had a much more profound effect on thermomechanical response as compared to changes in oligomer molecular weight in the molecular weight range investigated. This combination of chromatographic technique and thermomechanical analysis afforded an in-depth investigation of the structure–property relationships of urea-/urethane-containing photocurable oligomers.

Elastomers are a unique and important class of polymers that enjoy applications in virtually every industry, including healthcare, aerospace, automotive, and apparel. However, due to inherent physical, thermal, and mechanical properties of elastomers, the additive manufacturing (AM) of elastomers remains challenging. These challenges are discussed in the context of various AM processes, including powder bed fusion, material extrusion, and vat photopolymerization. This review provides an in-depth discussion of the current state of silicone and polyurethane polymers for AM, and also discusses polyesters/polycarbonates, liquid crystalline elastomers, and monomer compositions that provide elastomeric properties upon photocuring. Finally, the current state of common, commercially-available elastomers for AM is provided, as well as an outlook for this rapidly progressing field. We expect this review to be useful for any research involved with the additive manufacturing of elastomers.

Additive manufacturing, or three-dimensional (3D) printing, has emerged as a viable technique for the production of vascularized tissue engineering scaffolds. In this report, a biocompatible and biodegradable poly(tri(ethylene glycol) adipate) dimethacrylate was synthesized and characterized for suitability in soft-tissue scaffolding applications. The polyester dimethacrylate exhibited highly efficient photocuring, hydrolyzability, and 3D printability in a custom microstereolithography system. The photocured polyester film demonstrated significantly improved cell attachment and viability as compared with controls. These results indicate promise of novel, printable polyesters for 3D patterned, vascularized soft-tissue engineering scaffolds.