Acrylate systems, studies

The first nanoparticulate delivery system studied was Piloplex, consisting of pilocarpine ionically bound to poly(methyl)methacrylate-acrylic acid copolymer nanoparticles [44], Klein et al. [1,98] found that a twice-daily application of Piloplex in glaucoma patients was just as effective as three to six instillations of conventional pilocarpine eye drops. However, the formulation was never accepted for commercialization due to various formulation-related problems, including the nonbiodegradability, local toxicity, and difficulty of preparing a sterile formulation [208],... 

The system studied by this procedure was poly(styrene) as the host polymer and poly(methyl acrylate) or poly(butyl acrylate) as the blend polymers. The degradation rates were monitored by Py-GC. 

A polyurethane (PU)/poly(n-butyl methacrylate) (PBMA) system has been selected for an investigation of the process of phase separation in immiscible polymer mixtures. Within this system, studies are made of the XX, lx, xl, and the 11 forms. In recognition of the incompatibility of PBMA with even the oligomeric soft segment precursor of the PU, no attempt was made to equalize the rates of formation of the component linear and network polymers. Rather, a slow PU formation process is conducted at room temperature in the presence of the PBMA precursors. At suitable times, a relatively rapid photopolymerization of the PBMA precursors is carried out in the medium of the slowly polymerizing PU. The expected result is a series of polymer mixtures essentially identical in component composition and differing experimentally only in the time between the onset of PU formation and the photoinitiation of the acrylic. This report focuses on the dynamic mechanical properties cf these materials and the morphologies seen by electron microscopy. 

Particle Shape. The delineation of two families of materials on the basis of particle shape is very clear from the electron microscope evidence. That the families are xx, lx and xl, 11 points directly to the presence or absence of crosslinking in the PBMA as a source of particle shape differentiation. Overall concentration of the PBMA precursors is not a strong factor, since the irregular particles were observed in all three of the xx compositions, but an examination of the effect of crosslinker concentration alone was not carried out. In related work on an epoxy-butyl acrylate system in which component polymerization rates and the simultaneity of the reactions were matched, it was reported (3) that, prior to gelation of the matrix, irregular particles of crosslinked acrylate were formed but spherical particles were found in the absence of crosslinker. Together with the observation of an apparent bimodal size distribution, our results are similar, even though our system and conditions are markedly different from those in the earlier study. 

There are several interesting polymerization schemes intermediate between a sequential IPN and an SIN. For example, in in situ prepared sequential IPNs, both monomers are polymerized via free radical reaction [He et ai, 1993 Rouf et ai, 1994]. The two monomers must have quite different reactivities towards the free radicals. This situation arises with vinyl or acrylic double bonds and aUylic double bonds. The allylic double bonds react about 100 times slower than acrylic or methacrylic bonds. Often, two initiators are used, one reacting at a lower temperature, and the other at a higher temperature. In one of the systems studied, based on methyl methacrylate and diallyl carbonate of bisphenol-A (DACBA), first, crosslinked PMMA was formed at moderate temperatures. Then, by just increasing the temperature after completion of the first polymerization, the synthesis of the allylic network followed. 

The ethylene methyl acrylate system is amenable to low-temperature NMR mechanistic studies with all of the critical intermediates visible spectroscopically." " Acrylate insertion occurs predominantly in a 2,1-fashion, yielding a strained four-membered chelate ring in which the carbonyl oxygen atom is coordinated to the palladium atom. This insertion is followed by a series of /3-hydride eliminations and readditions expanding the ring stepwise to the six-membered chelate complex this is the catalyst resting state shown in Scheme 6. 

As has been shown above, the C02-induced reduction in kp,app amounts up to about 40%. It is interesting to see whether reactivity ratios, which determine copolymer composition, may also be affected by the addition of SCCO2. Special attention has been paid to copolymerization of such monomer pairs for which homopolymerization kp,app values are affected by CO2 in different ways, such as styrene-(meth)acrylate systems. In addition, acrylate-(meth)acrylate copolymerization systems were studied. 

The Rh(l)-catalysed asymmetric hydrogenation of various olefins (dehydroamido acids, enamides, itaconates, and acrylates) was studied in the presence of a wide range of enantiopure R-SMS-Phos = l,2-bis[(o-RO-phenyl)(phenyl) phosphino]ethane ligands where R was either branched or heteroatom-substituted alkyl, aralkyl, silyl, acyl, sulfonyl, and so on. The results indicated that the reaction rates increased by several times, with increased enantioselectivities, and this system was therefore better than DiPAMP = l,2-bis[(o-anisyl)(phenyl)phosphino]ethane ligand. ... 

F. De Candia, A. Taglialatela and V. Vittoria, Structure-Property Relationships in Some Composite Systems. Deformation Mechanism, J. Appl. Polym. Sci. 20, 1449 (1976). Simultaneous crosslinking of polybutadiene with polymerization of methacrylic acid or magnesium acrylate. Photoelastic study of hysteresis cycles. 

Substantial efforts have b n made to darify the structures of polyelectrotyte-sur ctant complexes in the last five years. " The systems studied so far induded poly(sodium acrylate) gel, poly(sodium methacrylate), poly(2-actylamido-2-methylpropanesulfonic acid) gel, polystyrenesulfonate or their copolymers interacting with all ltrimethytammonium bromide (CnTAB) and aikylpyridinium chloride (CJ CI) with n being the number of carbon atoms in the tail of the sur ctant. The lametlar, (ylindrical, and undulating byered structures were most commonly observed. 

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