No abstract

The properties of co-and terpolymers (physical, mechanical, chemical, biocompatibility, etc.) strongly depend on their microstructural details. In the course of our research work on biomaterials that feature intrinsic radiopacity, we became interested in the microstructural details of co-and terpolymers of methyl methacrylate (MMA), 2-hydroxyethyl methacrylate (HEMA), and 2-(2′-iodobenzoyl)-ethyl methacrylate (1) or 2-(4′-iodobenzoyl)ethyl methacrylate (2). A new method, based on 1 H-NMR at 400 MHz, was used to study the copolymerization reactions 1 + HEMA, 1 + MMA, 2 + HEMA, and 2 + MMA. This method was found to be convenient, fast, and accurate, and it is put forward that this approach can also be applied to study other copolymerization reactions. The results, obtained with the error-invariables method (EVM), are as follows: 1 + HEMA, r1 ) 1.09 ( 0.14, rHEMA ) 1.12 ( 0.06; 1 + MMA, r1 ) 0.54 ( 0.12, rMMA ) 0.67 ( 0.06; 2 + HEMA, r2 ) 2.18 ( 0.72, rHEMA ) 2.29 ( 0.38; 2 + MMA, r2 ) 0.93 ( 0.32, rMMA ) 0.90 ( 0.13. Based on these data, a triad analysis was performed. It is concluded that all four copolymerizations afford random-type macromolecules. Therefore, it is most likely that terpolymers consisting of 1 or 2, HEMA, and MMA will also have a random character. This conclusion is of interest, since it gives a better insight into the different biochemical and physicochemical properties of this type of co-/terpolymers. The results imply that random copolymers, built-up from a hydrophilic and a hydrophobic component, can also exhibit low thrombogenicity; this is in line with recent studies by Mathew et al. (Biomaterials 1993, 14, 57).

Lactide based polymers present a promising class of materials for successful development of fully resorbable stents, thus helping to bring the concept of vascular restoration therapies to life. Not only can these polymers be perfectly tuned to fulfil technical requirements for a fully resorbable stent, they have been proven to be safe materials with a long track record of in vivo biocompatibility in a broad range of medical and pharmaceutical fields. They have a strong regulatory history as well. The polymers degrade through hydrolysis, and are eliminated by the human body through natural pathways via the Krebs cycle. The polymers can perform a temporary mechanical function, allowing the tissue to heal and resume its original function before the implant looses its mechanical integrity. The mechanical performance of the stent can be achieved through stent design and manufacturing methods, as well as tailoring the properties of the polymer itself. The resorption time of cardiovascular stents based on these polymers can be tuned -from a polymer perspective- by tailoring the molecular weight, the crystallinity and the hydrophilicity of the polymer. Drug eluting coatings for resorbable stents can be developed from the same family of polymers, tailoring the composition to the desired controlled release of the applicable drug. To successfully develop resorbable cardiovascular devices an interdisciplinary approach is needed, bringing together polymer chemists and engineers and connecting them with medical device and clinical experts.