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

Abstract

Multiarm star copolymers, consisting of hyperbranched poly­(ethylene oxide) (hbPEO) or poly­(butylene oxide) (hbPBO) 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 (R,R)-(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.

Functional Polycarbonates from Carbon Dioxide and Tailored Epoxide Monomers: Degradable Materials and Their Application Potential

“…Successful conversion of the terminal hydroxyl groups with phenylisocyanate demonstrates the potential of such polycarbonate polyols for polyurethane synthesis. Furthermore, Frey and co‐workers studied amphiphilic and hydrophobic multiarm star polyols in a subsequent work using both hyperbranched poly(ethylene oxide) and hyperbranched poly(butylene oxide) polyether polyols as cores, and poly(propylene carbonate) and poly(butylene carbonate) as arms, respectively . Other groups investigated the synthesis of polycarbonate and poly(ether carbonate) based star and H‐shaped polymers with three to six arms .…”

“…Besides the use of functionalized monomers, the properties and functionality of aliphatic polycarbonates can also be controlled by the polymer architecture. The chain transfer reaction including externally added alcohols can be used for the incorporation of specific initiators or the synthesis of various polymer architectures such as block‐ or star‐like copolymers . In this respect, the epoxide/CO 2 copolymerization exhibits features typical of a living polymerization …”

Heterodinuclear complexes featuring Zn(ii) and M = Al(iii), Ga(iii) or In(iii) for cyclohexene oxide and CO2 copolymerisation

“…5 These polyols are used to manufacture a range of coatings, urethanes and thermosets which show equivalent or better properties than incumbent materials that derive only from petrochemicals. [6][7][8][9] Importantly, the process of CO 2 /epoxide copolymerisation to yield polycarbonate polyols is amenable to large-scale manufacturing. 5,10 Furthermore, life cycle analysis has shown a 'triple win' in terms of CO 2 emissions, for every CO 2 molecule incorporated into the polymer backbone, two more are saved by reducing epoxide consumption.…”

Anionic ring-opening copolymerization of styrene oxide with monosubstituted oxiranes: analysis of composition of prepared new copolyether-diols by MALDI-TOF mass spectrometry

“…The high M n polyether-triols, i.e., PO-EO copolymers, being the largest part of industrial production, are synthesized by polymerization of PO and/or EO initiated by eluent [1]. To modify the properties of the polyol component, copolymers are widely synthesized using anionic ring-opening copolymerization for propylene oxide and glycidol [15,16], propylene oxide and N,N-diethyl glycidyl amine [17], ethylene oxide and sulfonamide-activated aziridines [18] or ethylene oxide or butylene oxide with glycerol [19]. Also cationic ring-opening copolymerization can be performed [20].…”