Polycarbonates from Sugars:  Ring-Opening Polymerization of 1,2-O-Isopropylidene-d-Xylofuranose-3,5- Cyclic Carbonate (IPXTC)

Abstract

A number of applications in biomedical materials will greatly benefit by further research in bioresorbable polymers that have various side group attributes. By careful design, these functional groups can be used to regulate hydrophilicity/hydrophobicity, permeability, bioresorption and mechanical properties. 1-3 The pendant functional groups provide active sites for crosslinking and grafting as well as the opportunity to attach bioactive substances to modulate cellular responses for tissue engineering applications. 4-8 Aliphatic polycarbonates represent one family of bioresorbable materials that are being engineered for biomedical applications. [9][10][11][12] Various aliphatic polycarbonates, such as poly(trimethylene carbonate) (PTMC) 13 and poly(2,2-dimethyl trimethylene carbonate) (PDTC) 14 have been synthesized by ring-opening polymerization. Polycarbonates with hydroxyl pendant groups have been used to regulate bioresorption kinetics. For example, the in vitro degradation of PTMC in pH 7.4 buffer solution for 30 weeks at 37°C resulted in only a 9% weight loss and a 7% decrease in molecular weight. 13 In contrast, watersoluble poly(hydroxyalkylene carbonates) undergo rapid degradation even in neutral water. 15 Specifically, the intrinsic viscosity of poly[[(oxycarbonyl)oxyl]-1,4-threityl] decreased to ca. one-third of its original value within 14 days in phosphate-buffered saline at 37°C.Recently, we prepared the cyclic carbonate monomer 1,2-O-isopropylidene-D-xylofuranose-3,5-cyclic carbonate (IPXTC) from a natural sugar. This monomer was successfully copolymerized with lactide and also trimethylene carbonate. The result was the formation of copolymers that have ketal-protected hydroxyl side groups. 16,17 The ketal groups were hydrolyzed to give hydroxyl pendant groups. 16,17 The homopolymer of IP-XTC and its deprotected product (Scheme 1) would give a carbohydrate-based polymer with carbonate mainchain linkages. Due to the steric constraints around the carbonate of IPXTC, this monomer has thus far proved to be difficult to homopolymerize. Previously, it was only possible to obtain low molecular weight P(IPXTC) oligomers in poor yield by Sn(Oct) 2 catalyzed IPXTC homopolymerization. 16 In this paper, we report the successful use of anionic and rare-earth isopropoxide catalysts for IPXTC homopolymerizaton. Structural, thermal, and X-ray analyses of P(IPXTC) are described.IPXTC was synthesized by the method similar to that reported by Ariga et al., 18 exactly as was described elsewhere. 16,17 The general polymerization protocol and polymer characterization methods were also previously published. 16,17 Organometallic catalysts that contain aluminum, zinc and rare-earth metals as well as t BuOK were evaluated for their abilities to homopolymerize IPXTC. The results of this work are summarized in Tables 1 and 2. The catalysts MAO, AlEt 3 -H 2 O, ZnEt 2 -H 2 O, and Et 2 AlOEt are known as coordination-catalysts that are highly active for lactones, lactide, and TMC polymerizations. 1,[19][20][21][22] However, the ...

Synthesis, Characterization, and Degradation Behaviors of End-Group-Functionalized Poly(trimethylene carbonate)s

“…10,[26][27][28][29] Pendant hydroxyl groups have been introduced to improve the hydrophilicity and hence the degradability. 30 Since end groups have special effect on degradation rate, end-group functionalized polycarbonates will have different degradation rate. Because the polymers of multiarm architecture have a higher end-group concentration than linear polymers of the same molecular weights, the multiarm structure can strengthen the end group effect.…”

Synthesis, Characterization and In Vitro Cytotoxicity of Poly[(5-benzyloxy-trimethylene carbonate)-co-(trimethylene carbonate)]

“…[2] It is well known that copolymerization is an effective way of providing materials with different properties. The properties of PTMC also can be tailored by copolymerization of trimethylene carbonate (TMC) with other cyclic monomers, such as glycolide, [3] lactide, [4] e-caprolactone, [5] 1,4-dioxan-2-one, [6] cyclic phosphates, [7] as well as other cyclic carbonates, [8] in order to meet different needs.…”

The anionic ring-opening polymerization of five-membered cyclic carbonates fused to the cyclohexane ring

“…[1][2][3] For their synthesis, various procedures have been used, that is, (i) the polycondensation between the carbonate derivatives and diols, 4 (ii) the ring-opening polymerization of cyclic carbonates, [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] and (iii) the alternating polymerization of epoxides with carbon dioxide. Among these procedures, the ring-opening polymerizations of cyclic carbonates have the potential to control the molecular weight and to induce copolymerization with other cyclic monomers.…”

“…Six-membered cycles (or larger) using anionic initiators tend to polymerize smoothly, yielding the corresponding polycarbonate at a lower temperature (o100 1C). [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] In contrast, the anionic ring-opening polymerization of the fivemembered ring is thermodynamically unfavorable and proceeds at a higher temperature (4150 1C), causing the elimination of carbon dioxide to produce a copolymer that consists of both carbonate and ether linkages. [20][21][22][23][24][25] However, we reported that the anionic ringopening polymerization of a five-membered cyclic carbonate (MBCG) (Figure 1) possessing the a,D-glucopyranoside structure proceeded even at 0 1C to produce an aliphatic polycarbonate without the elimination of carbon dioxide.…”