PMA and PMMA

Most general purpose linear polymers, such as polyolefins, PS, PVC, and polymethyl methacrylate (PMMA), are not suitable for use at temperatures above 100 °C. PMMA and other polymers of 1,1-substituted vinyl monomers, such as poly-a-methylstyrene, decompose almost quantitatively to their monomers at elevated temperatures. However, the Tg and Tm values of these polymers are greater than those of polymers from 1-substituted vinyl monomers. For example, the Tg values of polymethyl acrylate (PMA) and PMMA are 276 and 381 K, respectively. 

PMMA is an illicit chemical compound that is a stmctural hybrid of PMA. PMMA and PMA are almost identical compounds. PMMA may also be marketed as ecstasy tablets. In humans PMMA has no known distinction from PMA in physiological effects. For the purpose of this informational entry, PMA and PMMA will be considered alike. 

By way of illustration we now discuss some results of Vilanove et al. ) for poly-(methyl acrylate) (PMA) at the air/water interface. These authors performed very accurate measurements on PMA (and PMMA) monolayers obtained by spreading small volumes = 30 of dilute solutions of PMA in chloromethylene. Taking extreme precautions to avoid impurities, they were able to measure surface pressures with a sensitivity of the order of a few pN m L Figure 3.94 shows a typical plot for the dilute regime, (0 < F< 0.02 pmoles m 2 and 10 < r < 100 pN m" ). 

In the current paper we extend previous work on poly(methyl acrylate) (9 - 10) and poly(methyl methacrylate) (9 - 11) in which the phosphorescence depolarization technique was shown to provide data which were consistent with reported dielectric and mechanical relaxation experiments, to the study of the molecular behaviour of poly(n-butyl methacrylate). This polymer, whilst of technological application, has received much lesser attention using conventional dynamic relaxation techniques than has been devoted to PMA and PMMA. In addition, fluorescence depolarization measurements have been employed in an attempt to provide complementary information regarding the higher frequency behaviour of the polymer. 

Motion of the dispersed naththalene triplet probe in P-Np is evident at 180K. By analogy with previous observations of the PMMA system(]Q) such mobility might be concomitant with the onset of the g-relaxation. It is apparent from dynamic mechanical data at IHz that resolution of the a and g relaxations is difficult(M). it may be that the use of molecular probes and labels such as 1-VN (as described above) offers a more sensitive sensory exploration of the matrix than is afforded by macroscopic techniques. It is also possible that the degrees of freedom for motion imbued in the matrix do not result from the motion of ester groups as generally inferred in PMA and PMMA for the g-relaxation but that conformational changes within the it-butyl substituent itself, constitute sufficient release of free volume within the matrix to allow rotational mobility of both the 1-VN label and the dispersed naphthalene probe. 

FIGURE 17.1 Absorbance cbanges of PMA- and PMMA-modified Composite 2 suspension with MeOH content in AcOEt/MeOH. 

The spiropyran unit has since been established as an effective molecular force probe. Following their initial discovery, the Moore group published detailed studies investigating the role of polymer architecture, mobility [16] and chain orientatiOTi [17, 18] in the mechanical response of PMA and PMMA, rubbery and glassy polymers, respectively, upon the application of tensile and torsional stress. A study by Beiermann et al. examined the fluorescence anisotropy of the ring-opened merocyanines as a means to characterise their degree of orientation relative to the direction of the applied tensile force. In PMA, they found strong preferential activation of the spiropyrans in the direction of the tensile force [17]. On tensile... 

Comparison of Acrylate with Methacrylate. The excursion temperature dependence of the increase in hole width for PMA and PMMA is shown in Figure 4. hi these polymers the rotation of the end methyl group has no influence on the microenvironments of the dyes and the rotation of the whole sidechain ester group... 

In these early years, the high energy radiation induced reactions of PMA and PMMA were not the only polyacrylates and polsrmethacrylates investigated, but they were foimd to be representative of the radiation chemistries of the two polymer families with different ester side-chains. 

The newest LFRP system involves reversible addition fragmentation chain transfer (RAFT) (259). PS, PMA, and PMMA having a polydispersity of < 1.3 and block copol5oners containing these monomers have been produced utilizing this novel chemistry. The initiators are either thioesters or thiocarbonates (260). The RAFT process is shown in Figure 48. 

The existence of an absorption at around 1430-1420 cm indicates the presence of an a-methylene (sometimes known as an active methylene), adjacent to the ester or ketone carbonyl. This, in conjunction with the presence of a normal aliphatic methylene sequence (1450-1470 cm ) differentiates the vinyl polymers, such as polyvinyl alcohol (PVA) and polyvinyl chloride (PVC), from compounds such as PMA and PMMA. Since this step may be confusing to the reader, it is suggested that attention is paid to the assignments for vinyl acetate-type and acrylate-type polymers. 

Sequential IPNs based on PMA and PMMA were prepared by UV photopolymerization [301]. The PMA/PMMA system is immiscible and so, for... 

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