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Poly(ethylene terephthalate), the fifth most produced polymer, generates significant waste annually. This increased waste production has spurred interest in chemical and mechanical pathways for recycling. The shift from laboratory settings to larger-scale implementation creates opportunities to explore the value and recovery of recycling products. Derived from the glycolysis of PET, bis(2-hydroxyethyl) terephthalate (BHET) exhibits versatility as a depolymerization product and valuable monomer. BHET exhibits versatility and finds application across diverse industries such as resins, coatings, foams, and tissue scaffolds. Incorporating BHET, which is a chemical recycling product, supports higher recycling rates and contributes to a more sustainable approach to generating materials. This review illuminates the opportunities for BHET as a valuable feedstock for a more circular polymer materials economy.

 

Thiol-acrylate photoresin containing dynamic disulfide bonds undergoes wavelength-selective photopolymerization under greenvs.UV light to produce a degradable step-growth networkvs.permanent chain-growth network.

 

The phosphine-substituted aryl diimine cobalt catalyst, (Ph2PPrADI)Co, has been found to mediate the dehydrocoupling of diamines or polyamines to poly(methylhydrosiloxane) (PMHS) to generate hydrogen and crosslinked solids in an atom-efficient fashion. The resulting siloxane diamine and siloxane polyamine networks persist in the presence of air or water at room temperature and can tolerate temperatures of up to 1,600 °C. Upon lowering the catalyst loading to 0.01 mol%, (Ph2PPrADI)Co was found to catalyze the dehydrocoupling of 1,3-propanediamine and PMHS (m = 35) to generate a siloxane diamine foam with a turnover frequency of 157 s-1 relative to diamine consumption, the highest activity ever reported for Si‒N dehydrocoupling. Furthermore, upon systematically reducing the number of potential branch points, the (Ph2PPrADI)Co catalyzed dehydrocoupling of diamines with hydride-terminated poly(dimethylsiloxane) (PDMS) was found to yield linear siloxane diamine polymers with molecular weights of up to 47,300 g/mol. 

Chain-transfer ring-opening metathesis polymerization (CT-ROMP) previously provided a route to carboxytelechelic polyethylene (PE) of controlled molecular weight; however, the incorporation of oligomeric PE into segmented copolymers remains unexplored. Herein, CT-ROMP afforded carboxytelechelic polycyclooctene segments, and subsequent reduction generated well-defined carboxytelechelic PE with M n = 3900 g mol −1 . Solvent-free melt polycondensation of neopentyl glycol and adipic acid with varying wt% telechelic PE oligomers yielded mechanically durable segmented copolyesters. The thermal and thermomechanical properties of the segmented copolyesters correlated with PE segment content, and high PE content copolymers exhibited remarkably similar morphologies and thermomechanical performance to conventional HDPE. The segmented copolyesters displayed advantageous physical properties while introducing susceptibility to chemo- and bio-catalytic depolymerization through periodic ester linkages, thus providing valuable fundamental understanding of an alternative route to HDPE. 

This manuscript describes the synthesis and characterization of guanine and cytosine‐containing supramolecular copolymers, which are inspired from the guanine and cytosine nucleobase pair in deoxyribonucleic acid. Regioselective Michael‐addition allowed the efficient installation of the nucleobases on acrylate‐containing monomers, which enabled the preparation of a series of nucleobase‐functionalized acrylate andn‐butyl acrylate copolymers using conventional free radical copolymerization. Guanine‐containing copolymers exhibited superior thermal properties, thermomechanical performance, and more defined morphological structure than cytosine‐containing copolymer analogs due to the relatively strong guanine self‐association, thus expanding the potential applications for mechanically reinforced polymeric networks. Blending guanine‐ and cytosine‐containing copolymers formed a supramolecular structure through multiple hydrogen bonding between guanine and cytosine units. The supramolecular blend exhibited intermediate thermomechanical and morphological properties, which suggested that guanine and cytosine units were not fully associated in the random copolymer composition. This work provides valuable fundamental understanding of structure–property‐morphology relationships in acrylic copolymers with the presence of guanine‐cytosine self‐ and complementary interactions, suggesting new understanding in supramolecular design for enhanced mechanical and morphological properties.

 

This work reveals the influence of pendant hydrogen bonding strength and distribution on self-assembly and the resulting thermomechanical properties of A-AB-A triblock copolymers. Reversible addition-fragmentation chain transfer polymerization afforded a library of A-AB-A acrylic triblock copolymers, wherein the A unit contained cytosine acrylate (CyA) or post-functionalized ureido cytosine acrylate (UCyA) and the B unit consisted of n-butyl acrylate (nBA). Differential scanning calorimetry revealed two glass transition temperatures, suggesting microphase-separation in the A-AB-A triblock copolymers. Thermomechanical and morphological analysis revealed the effects of hydrogen bonding distribution and strength on the self-assembly and microphase-separated morphology. Dynamic mechanical analysis showed multiple tan delta (δ) transitions that correlated to chain relaxation and hydrogen bonding dissociation, further confirming the microphase-separated structure. In addition, UCyA triblock copolymers possessed an extended modulus plateau versus temperature compared to the CyA analogs due to the stronger association of quadruple hydrogen bonding. CyA triblock copolymers exhibited a cylindrical microphase-separated morphology according to small-angle X-ray scattering. In contrast, UCyA triblock copolymers lacked long-range ordering due to hydrogen bonding induced phase mixing. The incorporation of UCyA into the soft central block resulted in improved tensile strength, extensibility, and toughness compared to the AB random copolymer and A-B-A triblock copolymer comparisons. This study provides insight into the structure-property relationships of A-AB-A supramolecular triblock copolymers that result from tunable association strengths. 

Vat photopolymerization (VP) and direct ink write (DIW) additive manufacturing (AM) provide complex geometries with precise spatial control employing a vast array of photo‐reactive polymeric systems. Although VP is recognized for superior resolution and surface finish, DIW provides versatility for higher viscosity systems. However, each AM platform presents specific rheological requirements that are essential for successful 3D printing. First, viscosity requirements constrain VP polymeric materials to viscosities below 10 Pa s. Thus, this requirement presents a challenging paradox that must be overcome to attain the physical performance of high molecular weight polymers while maintaining suitable viscosities for VP polymeric materials. Second, the necessary rheological complexity that is required for DIW pastes requires additional rheological measurements to ensure desirable thixotropic behavior. This manuscript describes the importance of rheological measurements when designing polymeric latexes for AM. Latexes effectively decouple the dependency of viscosity on molecular weight, thus enabling high molecular weight polymers with low viscosities. Photo‐crosslinking of water‐soluble monomers and telechelic oligomeric diacrylates in the presence of the latex enables the fabrication of a scaffold, which is restricted to the continuous aqueous phase and effectively surrounds the latex nanoparticles enabling the printing of otherwise inaccessible high molecular weight polymers. Rheological testing, including both steady and oscillatory shear experiments, provides insights into system properties and provides predictability for successful printing. This perspective article aims to provide an understanding of both chemical functionality (photo‐ and thermal‐reactivity) and rheological response and their importance for the successful design and evaluation of VP and DIW processable latex formulations.