Polyacrylates and Polymethacrylates

Polymethyl methacrylate (PMMA) degrades under irradiation and becomes more soluble due to main chain scission. The degradation can be greatly reduced by the addition of 10% of various additives, such as aniline, thiourea, or benzoquinone. PMMA is an example of a nongelling polymer it does not form a three-dimensional network structure under irradiation.  

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Kolarik, J. Secondary Relaxations in Glassy Polymers Hydrophilic Polymethacrylates and Polyacrylates Vol. 46, pp. 119—161. 

Secondary Relaxations in Glassy Polymers Hydrophilic Polymethacrylates and Polyacrylates... 

Dynamic Relaxation Behavior of Hydrophilic Polymethacrylates and Polyacrylates in the Glassy State... 

Polymethacrylates and polyacrylates have extensively been studied from the viewpoint of relaxations occurring in the glassy state. Though a vast amount of information has been collected to date, even a qualitative interpretation of the relaxation phenomena on a molecular level often remains questionable. This situation exists despite some favorable circumstances, i.e. polymethacrylates are amorphous polymers with comparatively simple molecular motions and it is possible to alter systematically their constitution and prepare various model polymers. 

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... 

Table 1. Polymethacrylates and polyacrylates measured - [CH2-CR,(COOR2)-] and their relaxation temperatures... 

With the exception of local main-chain motions, the above-mentioned types of molecular motions have been investigated on a series of hydrophilic polymethacrylates and polyacrylates by means of dynamic mechanical measurements carried out with a torsional pendulum. For this purpose, the constitution of polymethacrylates was systematically altered and correlated with the dynamic mechanical response spectra. It was established for a series of copolymers of poly(2-hydroxyethyl methacrylate) that the temperature of the y relaxation (140 K 1 Hz), assigned to the motion of 2-hydroxyethyl... 

The main advantage of this strategy is that aU the chains are end-capped by the functional initiator, at least in a strictly living process. However, the functional group attached to the initiator must be protected whenever it is sensitive to nucleophihc attack. A few examples of a-functional polymethacrylates and polyacrylates are reported hereafter. 

Methods of Separation. Elution Behavior. First, elution was performed by an isocratic elution mode. At a constant column temperature, the copolymers and homopolymers of polymethacrylates and polyacrylates were retained in the column with chloroform (and DCE) without ethanol. Only polystyrene could elute from the column. By adding ethanol to chloroform (and DCE), copolymers with a higher styrene content started to elute, and by increasing the ethanol content in the mobile phase, copolymers with less styrene were eluted. 

Polymethacrylic and polyacrylic acids give essentially no carbon dioxide under these conditions, while polymaleic acid (3ff) evolves 0.2 moles/monomer unit. Copolymers of itaconic and acrylic acid decarboxylate to produce an amount of carbon dioxide roughly corresponding. 

The effect of temperature on the flow behaviour of polymethacrylate and polyacrylate blends in mineral oil demonstrated that it is strongly controlled by the entropy of activation for viscous flow [51], confirming early speculations [52]. The increased negative entropy was presumably a result of the very sluggish translational motion of the polymer coils. On the other hand, the enthalpy of activation for viscous flow of the polymer solutions was, for the most part, very nearly the same as that of the oil solvent. Only the most efficient systems exhibited decreased enthalpy, suggesting that coil expansion at high temperatures may be a factor, but the effect was very small relative to the entropy effect. 

Graft copolymers were prepared by grafting polyfethyleneglycol monomethacrylate) (MPEG) onto polymethacrylate and polyacrylate copolymers via a transesterification reaction, using potassium methoxide as the transesterification catalyst [68]. The composition of the graft copolymers was chosen to lead to water soluble products. IR and XH-NMR spectroscopy and SEC were used to characterize the graft copolymers. 

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