Glass transition temperature polymethacrylates

Table 2. Glass-Transition Temperatures of Atactic, Syndiotactic, and Isotactic Polymethacrylate Esters,...

Atactic polymethacrylate esters, glass transition temperatures of, 16 273t Atactic polypropene, 16 104 20 524 Atactic polystyrene, 10 180, 182 Atactic propylene polymers, 17 704, 705 Atactic PSSA, 20 468 Atenolol, 5 102, 160... 

Syndiotactic polymerization, 76 99-102 Syndiotactic polymethacrylate esters, glass transition temperatures of, 76 273t Syndiotactic polypropylene, 20 524 Syndiotactic polystyrenes (SPS), 23 365 Syndiotactic polystyrene, 70 180-183 applications for, 70 183 properties of, 70 182... 

Polymerization. Poly (methyl methacrylate) was obtained commercially. The polymers of other methacrylates and their copolymers were prepared in toluene with 2,2 -azobisisobutyronitrile (AIBN) at 60 °C. All the polymers prepared free radically were syndiotactic or atactic. Isotactic poly(a,a-dimethylbenzyl methacrylate) was obtained using C6H5MgBr as the initiator in toluene at 0°C. Poly(methacrylic acid) was prepared in water using potassium persulfate at as the initiator 60 °C. The molecular weights, glass transition temperatures and tacticities of the polymethacrylates are summarized in Table I. 

Fig. 18. Viscosity (log rjinPa-s[lPa-s=10 pois]), as a function of temperature for polymethacrylate (a) PVC (b), and polyvinylacetate (c) according to Eq. (43) (WLF, theoretical curves). The diagram shows the great influence of the free volume near the glass transition temperature...

As mentioned earlier, we usually encounter two characteristic secondary relaxations in polymethacrylates and polyacrylates (below the glass transition temperature) which are assigned to side-chain motions1,12,13,15 The p relaxation due to partial rotation of... 

The temperature position of the secondary fi relaxation (about 290 K 1 Hz), generally attributed to partial rotations of the side chains COOR, is only slightly affected by the polarity and volume of the substituent R but decreases markedly (by 120 K) on removal of the a-methyl group on the main chain. The experimental data obtained contradict the assumption that there is a certain relationship between this temperature and the glass transition temperature. Nevertheless, we can infer that the pertinent molecular mechanism in polymethacrylates differs from that in polyacrylates, probably due to the different participation of the main chains. The values of the individual contributions to the activation energy were estimated by employing a procedure similar to that used in the y relaxation process, and their sum was found to agree approximately with the experimental values. 

The first pair of polymers (Figure 13.1) studied in our laboratory were the polyacrylate (pDRlA) and the polymethacrylate (pDRlM) derived from Disperse Red 1. Their glass transition temperatures were 91° and 129°C, respectively. Disperse Red 1 and the polymers derived from it have a maximum absorbance at about 480 nm. The actual maximum wavelength depends on the conditions, such as in film or in solution, and on the possibility of association of the chromophores. This absorbance is associated with the 7t - 7t transition of the trans azobenzene isomer. A thin film of one of the polymers can be subjected to laser irradiation (either 488 or 514 nm are close enough to the... 

In this study, we discussed the graded and miscible blend of polyvinyl chloride(PVC)/ polymethacrylate(polymethyl methacrylate(PMMA) or polyhexyl methacrylate(PHMA)) by a dissolution-diffusion method, and characterized graded structures of the blends by measuring FTIR spectra and Raman microscopic spectra, and thermal behaviors around the glass transition temperature(Tg) by DSC method, or by SEM-EDX observation. Finally, we measured several types of mechanical properties and thermal shock resistance of the graded polymer blends. 

Poly(methyl methacrylate (PMMA) is by far the predominant polymethacrylate used in rigid applications because it has crystal clear transparency, excellent weatherability (better than most other plastics), and a useful combination of stiffness, density, and moderate toughness. The glass transition temperature of the polymer is 105°C (221°F), and the heat deflection temperatures range from 75 to 100°C (167-212°F). The mechanical properties of PMMA can be further improved by orientation of heat-cast sheets. 

Samples of polymethacrylates mixed with PVC in ratios of 100 0, 5 95, 10 90, 15 85, 0 100 were examined on the Rheovibron. The relationships between the tangent of the dynamic mechanical loss angle and the temperature are shown in Figs. 5 and 6. From these data, the glass transition temperature regions were established for... 

Figure 8.32 Effect of side-chain iengths on the glass transition temperatures of polymethacrylates [O (S. S. Rogers and L. Mandelkem, J. Phys. Chem., 61, 985, 1957)] poly-p-alkyl styrenes [ (W. G. Bard, J. Polym. ScL, 37, 515, 1959)] poly-a-olefins [A (M. L. Dannis, J. Appl. Polym. ScL, 1, 121, 1959 K. R. Dunham, J. Vandenbergh, J. W. H. Falter, and L E. Contois., J. Polym. ScL, 1A, 751, 1963)] and polyacrylates [ (J. A. Shetter, Polym. Lett, 1, 209, 1963)] (139).

Table 8.12 Effect of tacticity on the glass transition temperatures of polyacrylates and polymethacrylates (141)...

Figure 5.4 Glass transition temperature of polyacrylates and polymethacrylates as a function of number of carbons ( ) in the oligo-methylene (R) group. Drawn after data from Rogers and Mandelkem (1957) (polymethacrylates) and Shetter (1963) (polyacrylates).

In four examples (3a-3d. 1U)le 2) of 13, an Sc phase was found. In the whole aeries the glass transition temperature (T,) decreases as the spacer length increases. An increase of T, occurs when passing horn tk polyacrylate to the polymethacrylates or the poly-chloroacrylates (Af G) due to the increasing stiffness of the polymer backbone. The effects oiX B and A G are nearly the same [12,13]. 

---