Glass transition temperature polyacrylates

The most common backbone structure found in commercial polymers is the saturated carbon-carbon structure. Polymers with saturated carbon-carbon backbones, such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyacrylates, are produced using chain-growth polymerizations. The saturated carbon-carbon backbone of polyethylene with no side groups is a relatively flexible polymer chain. The glass transition temperature is low at -20°C for high-density polyethylene. Side groups on the carbon-carbon backbone influence thermal transitions, solubility, and other polymer properties. 

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 acrylic plastics use the term acryl such as polymethyl methacrylate (PMMA), polyacrylic acid, polymethacrytic acid, poly-R acrylate, poly-R methacrylate, polymethylacrylate, polyethylmethacrylate, and cyanoacrylate plastics. PMMA is the major and most important homopolymer in the series of acrylics with a sufficient high glass transition temperature to form useful products. Repeat units of the other types are used. Ethylacrylate repeat units form the major component in acrylate rubbers. PMMAs have high optical clarity, excellent weatherability, very broad color range, and hardest surface of any untreated thermoplastic. Chemical, thermal and impact properties are good to fair. Acrylics will fail in a brittle manner, independent of the temperature. They will suffer crazing when loaded at stress about halfway to the failure level. This effect is enhanced by the presence of solvents. 

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... 

FIGURE 9.17 Dependence of productivity and separation factor /3p C6H5CH3/H2O of membranes based on various rubbery polymers on the glass transition temperature of the polymer (pervaporation separation of saturated toluene/water mixture, T = 308 K) (1) polydimethyl siloxane (2) polybutadiene (3) polyoctylmethyl siloxane (4) nitrile butadiene rubber with 18% mol of nitrile groups (5) the same, 28% mol of nitrile groups (6) the same, 38% mol of nitrile groups (7) ethylene/propylene copolymer (8) polyepichlorohydrin (9) polychloroprene (10) pol3furethane (11) polyacrylate rubber (12) fluorocarbon elastomer. (From analysis of data presented in Semenova, S.I., J. Membr. Sci., 231, 189, 2004. With permission.)... 

As can be seen from the last column of Table II, DSC studies did not indicate any change in the glass transition temperature of the polyacrylates due to the presence and/or concentration of the ionogenic monomer (SST) incorporated. We have observed the same behavior in styrene, methyl acrylate and other systems (26). Other workers have also reported similar results in ionomers synthesized by the direct reactions of various acrylic acid salts and covalent vinyl monomers (27). This indicates either the simultaneous homopolymerization of both monomers or a "block copolymerization. 

It is not necessary to carry out synthesis, if the triggering photochromic compound has good affinity to the polymer matrix. A mixture of the polyacrylate with BMAB which exhibits an excellent function as trigger is equally photoresponsive. While the monomer model compound (i.e. the acrylate before polymerization) does not provide a liquid crystalline phase, the polymer shows a clear nematic - isotropic transition at ca. 61 °C and the glass transition temperature at 24 °C as shown in Fig. 4. Tj j depends very much on the length of the alkyl spacer. In comparison with the... 

PVA is not suitable as the base of packaging materials since its physical and mechanical properties are impaired abruptly above the glass-transition temperature (28°C). It is used, nevertheless, along with polyvinyl butyral (PVB), polyvinyl alcohol (PVAL), alcohol-soluble polyamides and polyacrylates as a layer-carrier of Cl in multilayered films. The layer is formed via application of emulsions, suspensions or solutions of named polymers containing Cl onto the base film [23-26]. 

Table 15.7 Glass Transition Temperatures of Sample Polyacrylates...

Figure 6.19. Heat capacity, vs. temperature for polyurethane/polyacrylate SINs. Glass transition temperatures are indicated. ...

Table 6.6. Glass Transition Temperatures of Polyurethane/Polyacrylate SINs...

Weuts 1, Kempen D, Verreck G, Peeters J, Brewster M, Blaton N et al (2005) Salt formation in sohd dispersions consisting of polyacrylic add as a carrier and three basic model compounds resulting in very high glass transition temperatures and constant dissolution properties upon storage. Eur J Pharm Sd 25 387-393... 

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