In situ copolyesters containing polylactide (PLA) and polyhydroxyalkanoate (PHA) segments were obtained via ring-opening polymerization of L-lactide using PHA as a macroinitiator with stannous octoate as catalyst. Incorporation of PHA (20 wt %) into PLA affords a novel copolymer with Mn values ranging from 25 to 50 KDa and low polydispersities of 1.8-2.3. DSC analysis of the copolymer indicates well-defined crystallization and melting transitions different from the homopolymers and corresponding blend. The polymers were characterized by FT-IR, GPC, DSC, optical microscopy, NMR, and TGA. The results show successful reactivity of PHA as a macroinitiator for the ring-opening polymerization of lactide.

Oligoethylene-end-capped polylactides were synthesized through the ringopening polymerization of L-lactide with alcohol-terminated oligoethylenes as macroinitiators. The polymerization of L-lactide was carried out in bulk at 130 8C in the presence of stannous octoate and primary alcohols with four different molecular weights: 350, 425, 550, and 700 g/mol. The end-capped copolymers that formed had a number-average molecular weight of approximately 40,000 (weight-average molecular weight/number-average molecular weight ¼ 1.7) according to gel permeation chromatography and were highly crystalline in comparison with the similarly formed homopolymer of L-lactide. The copolymer structure was characterized by Fourier transform infrared, NMR, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and differential scanning calorimetry analysis. This work focused on developing more crystallizable and hydrolytically stable polylactide derivatives that could potentially be used as compatibilizers in polylactide-polyolefin blends or as nucleating agents for poly(L-lactide) or other polyesters. V V C 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5257-5266, 2005

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Poly(ester amide) copolymers based on L-lactide (2) and a new depsipeptide (1) were prepared by ring opening polymerization in the presence of Sn(Oct)2 as the catalyst. Variable monomer feed ratios up to 2.3 mol% 1 afforded copolymers containing ester and amido functional groups in the backbone. Lower glass transition temperatures and reduced crystallization kinetics and crystallinity compared to homo-polylactide (PLA) was achieved with low levels of amido incorporation. A reactivity comparison between enchainment of 2 and 1 was determined using in situ infrared spectroscopy. An increase in shear viscosity was observed with the increase of 1 content as determined by rheology studies. Cellular compatibility of the co-polymers was investigated by seeding D1 mouse stem cells onto films and characterizing cell morphology by optical microscopy. Preliminary results indicate that these novel materials exhibit reduced cell attachment compared to PLA and, pending further exploration, may have potential use in biomedical applications.

ABSTRACT:Three different supercritical fluids (SCF), CO 2 , dimethyl ether (DME), and propane, are investigated as potential solvents for processing two lactide-based terpolymers and two perfluorocyclobutyl (PFCB) aryl ether polymers. The repeat unit of the lactide-based terpolymers consists of a 1:1:1 ratio of l-lactide, diglycidyl ether of bisphenol A (DGEBA), and, in one case, 4,4Ј-hexafluoroisopropylidenediphenol (6F-Bis-A) and, in the other case, 4,4Ј-isopropylidenediphenol (6H-Bis-A). The PFCB-based polymers are synthesized from 1,1-bis[4-[(trifluorovinyl)oxy]phenyl]hexafluoroisopropylidene (6FVE) and from bis(trifluorovinyloxy)biphenyl (BPVE). For both classes of polymer the steric effect of the hexafluoroisopropylidene (6F) group reduces chain-chain interactions, disrupts electronic resonance between adjacent aromatic groups, and improves solubility. The two lactide-based terpolymers do not dissolve in CO 2 or propane, but dissolve in DME. At room temperature the poly(lactide 6F-BisA DGEBA) terpolymer dissolves at 700 bar lower pressure in DME compared to the poly(lactide 6H-Bis-A DGEBA) terpolymer. Although the 6FVE polymer dissolves in all three SCF solvents, pressures in excess of 800 bar are needed to dissolve this polymer in CO 2 and propane while 6FVE dissolves in DME at pressure below 150 bar. The other PFCB-based polymer (BPVE) only dissolves in DME, again at low pressure, although BPVE drops out of solution as the system temperature is raised above ϳ40°C, whereas 6FVE remains in solution in DME for temperatures up to 90°C.