To better understand protein/material and cell/material interactions at the submolecular level, well-defined polymer brushes consisting of poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) on silicon wafers were prepared by atom transfer radical polymerization (ATRP). Silicon wafers were treated with 3-(2-bromoisobutyryl)propyl dimethylchlorosilane (BDCS) to form a monolayer that acts as initiators for ATRP. Silicon-supported BDCS monolayers were soaked in a methanol/water mixture solution containing Cu(I)Br, bipyridine, and a sacrificial initiator. After MPC was added to the solution, ATRP was carried out for 18 h. The molecular weight and thickness of the PMPC brush layer on the silicon surface increased with an increase in the polymerization time. The dense polymer brushes were obtained by the "grafting from" system. By selective decomposition of the BDCS monolayer by UV light-irradiation, the PMPC brush region and the sizes were well controlled, resulting in fabricating micropatterns of the PMPC brushes. When the thickness of the PMPC brush layer was greater than 5.5 +/- 1.0 nm (3 h polymerization), serum protein adsorption and fibroblast adhesion were effectively reduced, i.e., proteins and cells could recognize such thin polymer brushes on the surface. In addition, the density of the adherent cells on the patterned PMPC brush surface could be controlled by changing the size of the pattern.

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A number of chemicals including carbon black, chitosan, benzalkonium chloride, sodium dodecyl sulfate, cyclodextrin, and zeolite13x were tested as odor-reducing fillers. The rationale is based on the concept of using odor absorbents/adsorbents for which both physical adsorption and chemical adsorption play an important role in odor reduction. The fillers were incorporated into highly odorous natural rubber (STR20 and RSS5) by physical mixing prior to sulfur vulcanization. As identified by gas chromatography and gas chromatography/mass spectrometry, the unpleasant odor mainly originates from low molecular weight volatile fatty acids. The quantity of acetic acid, a representative of odor molecule, can be significantly reduced in the presence of chitosan and zeolite13x. Although carbon black and cyclodextrin exhibited a tendency to reduce the odor, they were not as effective as zeolite13x and chitosan. On the other hand, commercial surfactants such as benzalkonium chloride and sodium dodecyl sulfate cannot serve as odor-reducing substances because of their limited thermal stability. An olfactometry test confirmed that chitosan and carbon black are good odor-reducing agents. Chitosan and carbon black showed a reinforcing effect on vulcanized rubber, whereas the surfactant deteriorated the strength of the rubber composite.

This work is a part of a series on surface modification of materials made of chitosan. This report focused on grafting monomethoxy ethylene glycol oligomers (mPEG) on the surface of chitosan films. The chemical reactions were performed by immersing the films in organic solvent containing aldehyde derivative of mPEG. The presence of ethylene glycol moieties was determined by attenuated total reflectance‐infrared spectroscopy (ATR‐IR) and nuclear magnetic resonance (NMR). The hydrophobicity of the modified surface, determined by air‐water contact angle, decreased when the ethylene glycol derivatives were grafted on the film. The modified films were also subjected to protein adsorption study in order to assess their uses in biomedical applications. It was found that the presence of ethylene glycol units reduced the adsorption of proteins (albumin and lysozyme) on the films. We therefore have shown that manipulation of the interaction between chitosan and bio‐macromolecules is possible by chemically modifying the surface of chitosan.

Tyrosine‐derived polycarbonates having carboxylic acid pendant groups were characterized by water contact angle and X‐ray photoelectron spectroscopy (XPS). A pronounce decrease of receding angle as well as contact angle hysteresis as a function of acid composition strongly indicated that the acid groups are more accessible at the water/polymer interface after hydration. pH dependent contact angle confirmed an existence of carboxylic acid groups in the surface region. The receding angle transition appearing in the pH range of 4‐6 was a consequence of hydrophilicity change due to interconverting from carboxylic acid (‐COOH) to carboxylate ion (‐COO−). The surface compositions of imidazole‐labeled polymers as analyzed by XPS were consistent with the bulk stoichiometry of the polymers. Reactivity of acid groups towards chemical reaction at the surface was also investigated. The acid groups at the surface of polymers were capable of adsorbing a significant amount of calcium ion from simulated body fluid and being activated by a reaction with N‐hydroxysuccinimide.

Odorous components emitted from different forms of solid natural rubber (NR) were analyzed using gas chromatography (GC) and gas chromatography/mass spectrometry (GC/MS) associated with head space sampling technique. The most odorous components from most samples were identified as low molecular weight volatile fatty acids (C2-C5). Other volatile organic contents verified based on characteristic ions of mass spectra included carbonyl compounds, low molecular weight compounds containing nitrogen or sulfur and aromatic compounds. The total content and composition of volatile organic compounds were directly correlated to the rubber quality and drying process. Low-grade NR samples, i.e. STR 20 from cup lumps with intense smell, had high quantity of volatile organic contents especially low molecular weight volatile fatty acids. On the other hand, high-quality rubber, i.e. deproteinized NR and STR 5L from which no smell was detected, contained only minute quantities of volatile organic contents. Aromatic components were regarded as other major odorous contents found in ribbed smoked sheet (RSS) samples. The results suggested that the odorous components were the by-products of non-rubber components which had undergone microbial breakdown during storage or thermal degradation during processing.