Rigid Hyperbranched Polycarbonate Polyols from CO₂ and Cyclohexene-Based Epoxides

Hyperbranched, multifunctional polycarbonate polyols based on CO₂, cyclohexene oxide (CHO), and the “inimer” (initiator–monomer) (4-hydroxymethyl)­cyclohexene oxide (HCHO) were prepared in one-pot syntheses. The related linear poly­(hydroxymethyl cyclohexene carbonate) structures based on protected HCHO and postpolymerization deprotection were also synthesized as model compounds. The content of hydroxyl functionalities was adjustable for both linear and hyperbranched terpolymer systems. All CO₂/epoxide polymerizations were catalyzed by the (<i>R</i>,<i>R</i>)-(salcy)-Co­(III)­Cl complex. The polycarbonates obtained were comprehensively investigated using various 1D and 2D NMR techniques, SEC, FT-IR, UV–vis spectroscopy, and contact angle measurements. Rigid polyols with molecular weights between 3600 and 9200 g mol^–1 and moderate dispersity between 1.18 and 1.64 (<i>M</i>_w/<i>M</i>_n) were obtained. In addition, the materials were examined with respect to their thermal properties, intrinsic viscosity, and their three-dimensional structure. Glass transition temperatures in the range of 113–141 °C (linear) and 72–105 °C (hyperbranched) were observed. The intrinsic viscosity of the hyperbranched systems is in the range of 5.69–11.51 cm³ g^–1 and mirrors their compact structure. The hyperbranched polyols were also studied regarding their successful reaction with phenyl isocyanate to convert the free hydroxyl groups into urethanes

Multiarm Polycarbonate Star Polymers with a Hyperbranched Polyether Core from CO₂ and Common Epoxides

Multiarm star copolymers, consisting of hyperbranched poly­(ethylene oxide) (<i>hb</i>PEO) or poly­(butylene oxide) (<i>hb</i>PBO) polyether copolymers with glycerol branching points as a core, and linear aliphatic polycarbonate arms generated from carbon dioxide (CO₂) and epoxide monomers, were synthesized via a “core-first” approach in two steps. First, hyperbranched polyether polyols were prepared by anionic copolymerization of ethylene oxide or 1,2-butylene oxide with 8–35% glycidol with molecular weights between 800 and 389,000 g·mol^–1. Second, multiple arms were grown via immortal copolymerization of CO₂ with propylene oxide or 1,2-butylene oxide using the polyether polyols as macroinitiators and (<i>R</i>,<i>R</i>)-(salcy)-CoCl as a catalyst in a solvent-free procedure. Molecular weights up to 812,000 g·mol^–1 were obtained for the resulting multiarm polycarbonates, determined by online viscometry with universal calibration and ¹H NMR. Comparing the synthesis of different multiarm star polycarbonates, a combination of a highly reactive macroinitiator with a less reactive epoxide monomer was found to be most suitable to obtain well-defined structures containing up to 88 mol% polycarbonate. The multiarm star copolymers were investigated with respect to their thermal properties, intrinsic viscosity, and potential application as polyols for polyurethane synthesis. Glass transition temperatures in the range from −41 to +25 °C were observed. The intrinsic viscosity could be adjusted between 5.4 and 17.3 cm³·g^–1 by varying the ratio of polyether units and polycarbonate units

Biobased Thermoplastic Elastomers Derived from Citronellyl Glycidyl Ether, CO₂, and Polylactide

Biodegradability and biobased feedstocks are key requirements for sustainable materials. This work presents the synthesis of PLLA-b-PCitroGEC di- and triblock copolymers [PCitroGEC: poly(citronellyl glycidyl ether carbonate)] as degradable thermoplastic elastomers (TPEs), sourced from biorenewable feedstocks. l,l-Lactide (LLA) is produced by the fermentation of corn or sugar on a large scale, while citronellol can be extracted from rose or lemon grass. A key feature of the current TPE structures is their low glass temperature (Tg) of the highly flexible polycarbonate midblock, based on PCitroGEC. The latter was synthesized by catalytic copolymerization of CO2 and citronellyl glycidyl ether, using (R,R)-(salcy)-Co(III)Cl (CoSalenCl) and bis(triphenylphosphine)iminium chloride ([PPN]Cl) as a catalyst system. The resulting PCitroGEC macroinitiators (11,000 to 26,000 g·mol–1, DMF) were used in a DBU-catalyzed ring opening polymerization of LLA, resulting in a series of PLLA-b-PCitroGEC triblock copolymer structures. Molar masses range between 18,000 and 41,000 g·mol–1, with the molar fraction of the “soft” PCitroGEC block varied between 22 and 60 mol %. Glass temperatures of the block copolymers were studied with a combination of temperature-modulated differential scanning calorimetry and dielectric spectroscopy techniques. Small-angle X-ray scattering (SAXS) confirmed nanophase separation for all synthesized TPEs. SAXS was further employed to construct the PLLA-b-PCitroGEC-b-PLLA phase diagram. It comprises classical phases (spheres, cylinders, and lamellae). Tensile testing illustrated elastic properties for all TPEs with elongation at break up to 600% and almost no plastic deformation for copolymers with a PCitroGEC content above 31 mol %. Cyclic tensile tests confirmed the elastic recovery properties of the TPEs. Furthermore, the materials exhibited low E-moduli of 0.15–1.0 MPa, rendering PLLA-b-PCitroGEC-b-PLLA triblock copolymers suitable for potential use in soft tissue engineering