A large-molecular-weight polyanion is found to possess lubricating properties for cartilage. The polyanion, sodium poly(7-oxanorbornene-2-carboxylate), is synthesized by ring-opening metathesis polymerization of methyl 5-oxanorbornene-2-carboxylate. When dissolved in aqueous solution and applied to the surface of human cartilage it reduces the friction at the interface and acts as a lubricant. Its performance is similar to that of synovial fluid and superior to those of saline and Synvisc in an ex vivo human cartilage plug-on-plug model. The polymer is also not readily degraded by hyaluronidase or cytotoxic to human chondrocytes in vitro. As such, this polymer is a new type of viscosupplement, and the results provide insight into the design requirements for synthesizing highly efficacious synthetic biolubricants.

Surface-initiated ring-opening metathesis polymerization of cyclooctadiene (COD), a low ring-strain olefin, is reported for the first time. Polymerization was carried out in the vapor phase, which is advantageous compared to conventional solution methods in terms of minimizing chain transfer by reducing polymer chain mobility at the vapor/solid interface. Attachments of a norbornenylcontaining silane and a Grubbs catalyst to silicon substrates were carried out before samples were exposed to COD vapor. The thickness of grafted 1,4-polybutadiene films was controlled by reaction time and reached ~40 nm after 7 h. The polymer films were further chemically modified to afford a new polymer, head-to-head poly(vinyl alcohol).Polymer thin films have attracted significant interest because of their application in nanopattern fabrication, 1 preparation of "smart" materials, 2 chemical sensing, 3 and separations. 4 Surface grafting methods have been employed to covalently attach polymer films to various inorganic substrates. 5 Among different approaches, surface-initiated ring-opening metathesis polymerization (SiROMP) is an effective method to tether polymer chains to substrates including gold, 6,7 silicon wafers, 8-11 steel, 12 silicon (111), 13 and silica nanoparticles. 14 SiROMP has been used to prepare organic dielectric layers for the construction of field effect transistors; layer thickness has been controlled from less than 100 nm to more than 2 μm. 6 This technique has also been widely used to form a variety of patterned polymer films. 8,11 To the best of our knowledge, the monomers undergoing SiROMP have been limited to norbornene 6,14 and its derivatives; 15 there is no report on SiROMP of low-strain cyclic monomers, such as cis,cis-cycloocta-1,5-diene (COD), due to extensive chain transfer during polymerization.Here we report a versatile approach to SiROMP of this low-strain cyclic monomer in the vapor phase and the subsequent chemical modifications of the grafted polybutadiene (PBd) thin films. Reduced polymer chain mobility at the vapor/solid interface minimizes chain transfer in polymerizations carried out in the vapor phase. The vapor phase also provides an efficient method for new materials synthesis -a new polymer, head-to-head poly(vinyl alcohol) (hh-PVOH) was prepared using oxidation/hydrolysis of the grafted PBd.The 2 nd generation Grubbs catalyst was chosen as the initiator for the SiROMP of COD on silicon wafers due to its high reactivity and tolerance to water, oxygen, and functional groups. As shown in Scheme 1, the catalyst was attached to silicon surfaces through a norbornenyl monolayer which was prepared in the vapor phase from norbornenyltriethoxysilane at 70 °C. The norbornenyl groups have high ring strain and can readily react with the catalyst. Closely E-mail: weichen@mtholyoke.edu. NIH Public Access Author ManuscriptLangmuir. Author manuscript; available in PMC 2008 August 13. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript packed norbornenyl groups, however...

An efficient and general synthetic strategy for the preparation of high-molecular-weight hydrophilic polymers bearing both carboxylic acid and hydroxyl pendant groups is described. Specifically, poly(5,6-dihydroxyoxanorbornane carboxylic acid) with molecular weight ranging from ∼100 000 to 5 000 000 g/mol was prepared by ring-opening metathesis polymerization of methyl 5-oxanorbornene-2-carboxylate in the presence of Grubbs catalyst II and subsequently modified to tune the hydrophobic/hydrophilic properties by the introduction of either hydroxyl or carboxylic acid functionalities. These polymers mimic the natural acidic polysaccharide alginate and form hydrogels with polylysine. These polymers belong to a class of carbohydrate-like polymers, which are of interest for investigating the relationships between chemical structure and rheological properties as well as for providing new synthetic polysaccharide substitutes for applications in the biotechnology and pharmaceutical industries.

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