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Some novel polymeric fibrous nonwoven meshes have been processed from solution blends of poly(L-lactide-cocaprolactone), P(LL-CL), and gelatin for use as biodegradable porous scaffolds in articular cartilage tissue engineering. P(LL-CL) copolymers with LL:CL compositions ranging from 50:50 to 80:20 mol% were synthesized via the bulk ring-opening copolymerization of L-lactide (LL) and e-caprolactone (CL) using tin(II) octoate, Sn(Oct) 2 , as the initiator. To make the hydrophobic P(LL-CL) more hydrophilic for cell culture, it was solution blended with gelatin using trifluoroethanol as a common solvent to give P(LL-CL):gelatin contents in the final scaffolds ranging from 70:30 to 95:5 wt%. Two different processing methods were used: electrospinning and wet spinning. Although electrospinning gave a more uniform mesh of nanosized fibers, the nonwoven mesh from wet spinning with its much larger pores and greater pliability was found to be more suitable for water absorption, cell infiltration and shape-forming. Scanning electron micrographs of the scaffolds from the two techniques are compared. From the results obtained, the wet-spun P(LL-CL)50:50/gelatin 95:5 scaffold gave the best combination of properties. In particular, the 5% gelatin content resulted in a fivefold increase in the scaffold's equilibrium water uptake from about 10% to over 50% by weight. POLYM. ENG. SCI., 57:875-882, a LL:CL ratios are the comonomer feeds (mol%) used in synthesis. b LL:CL ratios are the actual copolymer compositions (mol%) from 1 H-NMR. c PDI 5 polydispersity index 5 M w /M n (where M w and M n have units of g/mol). d DSC data obtained from second heating scan. e T g determined by dynamic mechanical analysis (DMA): temperature scan from 280 to 1008C at 28C/min, frequency 1 Hz, on thin film sample in tension mode. f 50:50 copolymer was completely amorphous with no observed T c or T m transitions.

Styrene-maleic acid (SMA) block copolymers with either acrylamide (AM) or N,N-dimethylacrylamide (DMA) have been synthesized via a 3-step process comprising: (1) photopolymerization of styrene and maleic anhydride in solution to yield an alternating styrene maleic anhydride (SMAnh) copolymer,(2) copolymerization of SMAnh with either AM or DMA to yield SMAnh-b-AM and SMAnh-b-DMA block copolymers and (3) hydrolysis of the anhydride groups to yield water-soluble SMA-b-AM and SMA-b-DMA block copolymers as the final products. With a view to their intended application in membrane protein solubilization, molecular weights are controlled to below 10,000 by the synthesis conditions employed in step (1), including using carbon tetrabromide (CBr 4 ) as a chain transfer agent. The CBr 4 also plays an important role in step (2). By terminating the SMAnh chain radicals from step (1) with C-Br bonds that are photolytically active, SMAnh chain radicals can be regenerated to act as macroinitiators for the polymerization of AM or DMA in step (2). Finally, following step (3) and due to the pH-dependency of the SMA chain conformation in solution, a pH of 7-8 is found to be optimal for enabling the final products to be precipitated in a solid form that is completely soluble in water.

This paper describes the molecular design of a speciality polyester for use as a fast-absorbable monofilament surgical suture. In the surgical context, fast-absorbable means tensile strength loss within a period of 10-14 days, the minimum period required for secure wound approximation, after which the suture gradually loses its mass integrity leading to complete mass loss within 2-3 months. In order to be fast-absorbable, it is necessary that the main monomer used in synthesizing the polymer is glycolide since the polymer repeating unit, -OCH2CO-, is the chemical structure which hydrolyses the most rapidly in the human body. However, glycolide alone would give a monofilament suture fibre which would be too stiff and unwieldy for practical purposes and so it needs to be copolymerised with other cyclic ester monomers such as L-lactide and caprolactone to modify its mechanical properties. In this way, a monofilament fibre can be obtained which has an appropriate balance of hydrolysability and flexibility. Thus, this work enters the realm of molecular engineering insofar that it involves the strict control of both the chemical and physical microstructure of the polymer during the synthesis and processing steps respectively. This paper will describe how this controlled molecular architecture can be achieved and some preliminary results will be presented.