Abstract
For the first time, ring-opening metathesis polymerization of novel 7-membered cyclic phosphate monomers and their copolymerization with cyclooctene is presented. The monomers were investigated with respect to their metathesis behavior with different Grubbs catalysts and it was found that the Grubbs third generation catalyst gives the best results resulting in polymers with a molecular weight of up to 5000 g mol−1. Also copolymers with cyclooctene (up to a molecular weight of ca. 50 000 g mol−1) were synthesized and the monomer ratios were varied. The degree of polymerization could be controlled and the polydispersity index was usually below two. Acidic hydrolysis of the copolymer showed a complete shift of the molecular weight distribution to higher elution times in SEC, indicating a random incorporation into the poly(cyclooctene) backbone of the phosphate monomers and the possible degradation of the phosphate bonds along the backbone. Further, potentially degradable nanoparticles were prepared by a solvent evaporation miniemulsion technique.
Highlights
Degradable polymers are a growing eld in modern materials science due to limitation of natural resources and due to the long half-life times of commodity plastics in nature.[1]
We recently developed a route towardssaturated hydrophobic PPEs via acyclic diene metathesis polymerization (ADMET) of several phosphate monomers and we are currently investigating their performance in bioapplications.[4]
In summary we were able to synthesize novel seven-membered cyclic phosphates which can be applied to the synthesis of degradable PPEs and copolymers with cyclooctene via ring opening metathesis polymerization (ROMP)
Summary
Degradable polymers are a growing eld in modern materials science due to limitation of natural resources and due to the long half-life times of commodity plastics in nature.[1] for the biomedical eld, for example as drug carriers, in tissue engineering or when renal clearance of (macro)molecules is necessary, degradable – or partly degradable – polymers are of high interest.[1,2] Within the eld of degradable polymers, polyesters are the most common materials with poly(lactide) probably being the most prominent example.[2,3] In recent projects, we have been focusing on the development of novel potentially biodegradable and biocompatible polyphosphoesters (PPEs).[4] PPEs can be degraded by several enzymes such as phosphatases and phosphodiestereases and/or by basic or acidic hydrolysis.[5,6] In spite of this obvious bene t, PPEs are only scarcely found in recent studies, even if they are accessible and allow the feasible synthesis of a great variety of (functional) materials.[6] In contrast polyesters based on carboxylic acids face the problem that functional cyclic lactones require multi-step syntheses or conventional polycondensation needs to be applied which excludes many functional groups and limits the molecular
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