Chemical environment PMMA

Finally, Vahahi et al. calculated the contributions of the phosphonate group for two chemically modified PMMAs. Significant differences were found between both molecular structures. This result confirms that the contributions of phosphorus-containing groups could hardly be calculated while their effects depend on their chemical environment. 

The interaction between PMMA chains in the hybrid polymer prepared from 2mol% Zr402(OMc)i2 and MMA was investigated by dielectric spectroscopy and a predominant syndiotactic conformation of PMMA chains was found. " Comparison with the spectra of syndiotactic and isotactic PMMA clearly indicated that in the hybrid network the macromolecular chains experience a different chemical environment than in cluster-free PMMA. The results suggest that in the hybrid polymer the organic chains are more separated from each other, owing to the cluster crosslinks. This results in less pronounced interchain interactions. 

The degradation of chemically pure PMMA in nitrogen and oxygenated environments concluded that mass-loss rate measurements in pure nitrogen can be modelled as a three-step reaction - the first and second steps were minor steps and the third was a major one [a.4, a.426] 893911. As oxygen fraction increased to 5% O2 in N2, the degradation... 

Studies of polymers such as polymethylemethacrylate (PMMA), polyethylenetherephthalate (PET) and polytetrafluoroethylene (PTFE) revealed that the chemical surface changes depend considerably on the laser fluence, the nature of the environment surrounding the polymer during the treatments and the UV absorption coefficient of the polymer (6.7.81. It was found that the Ablative... 

McCarely et al. [219, 220] described a simplified photomodification protocol of PMMA and PC substrates through direct and controlled UV exposure of the substrates in an oxygen-rich environment to yield surface carboxylic acid moieties. Patterns of carboxylic acid sites could be formed by exposure of the polymers in auto UV irradiation at 254 nm with a power density of 15 mW/cm for 60 min without significant physical damage to the polymer surface. The so-formed chemical patterns allowed for further functionalization to yield arrays or other structured architectures through covalent attachment chemistry. 

The technical routes of the commercialized processes of PMMA could be categorized by (i) the direct oxidation process which consists of catalytic oxidation of isobutylene or tert-butanol to methacrylic acid (MAA) in two steps (ii) the methacrylonitrile (MAN) route by ammoxidation of tert-butanol (iii) the BASF s method which employs ethylene, carbon monoxide, and formaldehyde as raw materials (iv) the new ACH process by Mitsubishi Gas Chemical Co. Inc., which does not generate acid waste and (v) the direct oxidative esterification of methacrolein by Asahi Chemical Co. Ltd.[l] For most of the newly developed processes, efforts have been made to minimize the impact of the production on the environment. 

Polymers used for engineering purposes tend to be relatively resistant to chemical attack, but the strength of certain polymers can fall dramatically in the presence of particular environments through the process of environmental stress cracking. The problem is very specific to certain polymer environment combinations such as PMMA with alcohols and polyalkenes in detergents and can lead to premature failure at very low stresses through either plasticization or a reduction in surface energy. 

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