Facile one-spot synthesis of highly branched polycaprolactone

Abstract

Reported is the first solvent-free (bulk) synthesis of degradable/bioresorbable, highly branched polymers via tin octanoate Sn(Oct 2 ) catalysed controlled ring opening copolymerisation (ROP) of mono and di-functional lactone monomers that proceed to near quantitative conversion. The successful isolation of solvent soluble, highly branched structures was shown to be dependent on both the concentration of the di-functional monomer and the overall reaction time. Comparison with analogous systems utilising controlled radical polymerisation (CRP) to form the highly/hyper branched polymers suggested significant experimental differences between the two chain growth methods. The maximum proportion of di-functional monomer without gelation ensuing was found to be 0.6 equivalents w.r.t. mono-functional monomer (c.f. 1 with CRP) and the onset of significant levels of branching occurred at approximately 90% conversion (c.f. ~70% with CRP). These differences and significant disparity in reaction times were attributed to (a) the coordination and insertion (C+I) propagation mechanism adopted by the Sn catalyst and (b) the presence of additional trans-esterification reactions at high conversion. Evidence is presented to support the conclusion that there are two mechanisms contributing to the overall branching process in the ROP system at high conversion. First, the C+I mechanism promotes growth of linear polymer until approximately 90% conversion, after which both the C+I and transesterification processes contribute to the interchain branching process. The branched nature of the molecular structures was supported by confirmation plots generated from static light scattering. This data demonstrated that the polymers synthesised exhibit varying degrees of branching, consistent with the di-functional monomer (4, concentration in the feed. The degree of branching was calculated using 3 different methods 2 and the results were shown to be independent of method. Finally, DSC analysis of the polymers demonstrated correlation between the degree of branching achieved and the observed T m for the material where increased branching leads to a drop in the recorded T m .

Highly Branched Polycaprolactone/Glycidol Copolymeric Green Plasticizer by One-Pot Solvent-Free Polymerization

“…Recently, Irvine et al. successfully prepared highly branched PCLs using 4,4′-bioxepanyl-7,7′-dione (BOD) as a branching agent . In this work, PCLs with a well-defined branching structure were achieved via one-pot bulk copolymerization of CL and BOD in the presence of commercially relevant tin 2-ethylhexanoate (Sn­(Oct) 2 ) catalyst.…”

The synthesis and characterization of multiarm star-shaped graft copolymers of polycaprolactone and hyperbranched polyester

“…A signal at 3.4 ppm is assigned to the terminal -CH 2 -OH of PCL [17]. If water is present (sample BH40g5) the triplet changes to the doublet of triplets.…”

“…In recent years there is an increasing interest in the synthesis of three, four, six and multi-arm star-shaped [10][11][12][13][14][15] and hyperbranched (HB) [16][17][18][19] polycaprolactone polymers and copolymers. Star polymers have better solubility, and lower viscosity, melting temperature, and degree of crystallization than their linear analogues.…”

Sn(ii)-catalyzed β-citronellol esterification: a Brønsted acid-free process for synthesis of fragrances at room temperature

“…9,10 In this regard, tinIJII) chloride is an inexpensive and easy to handle solid catalyst that could be more potentially active in acid-catalyzed reactions. [11][12][13][14][15] The development of selective processes to functionalize monoterpenes based on commercial and simple metal catalysts is a goal that has been pursued by our research group. 16,17 Recently, tinIJII) halide catalysts have been successfully tested in the ketalization and esterification reactions of fatty acids and glycerol.…”