Triphenylmethyl methacrylate copolymers

A similar improvement in sensitivity via copolymerization was observed in the copolymers of methyl methacrylate with a,a-dimethylbenzyl methacrylate (Table VI) and triphenylmethyl methacrylate (Table VII). In the former case the mechanism of sensitivity enhancement should be the same as that for the poly(a,a-diphenylethyl methacrylate-co-methyl methacrylate), although the enhancement of sensitivity with copolymerization is rather low. 

The homopolymer of triphenylmethyl methacrylate is not soluble in usual organic solvents but it is solubilized by the incorporation of methyl methacrylate units. The copolymers containing over 90 mol% methyl methacrylate are soluble in the organic solvents such as toluene and xylene. In... 

Table VII the electron-beam exposure characteristics are given for the soluble poly (triphenylmethyl methacrylate-co-methyl methacrylate)s. The sensitivity on alkaline development was strongly influenced by the copolymer composition. The highest sensitivity was obtained on the copolymer containing 93.7 mol% methyl methacrylate. The copolymer of highest sensitivity showed the 7-value of 6.3, which was nearly twice as large as that for poly(methyl methacrylate). Formation of methacrylic acid units on exposure is obvious from the infrared spectrum. However, the mechanism of the occurrence should be different from the case of the a,a-dimethylbenzyl methacrylate polymer since there are no /3-hydrogen atoms in the triphenylmethyl group, and may be similar to the case of poly (methyl methacrylate). This will be explored in the near future.

Triphenylmethyl methacrylate (TrMA) and azobenzene-modified methacrylates were randomly copolymerized in toluene at — 78°C with chiral catalysts to give optically active helical copolymers (19 in Fig. 6) [65]. The optical activity (optical rotation) of the copolymers decreased with the increasing content of the azobenzene-modified methacrylates in the copolymers. The single helical conformation of PTrMA is quite stable in solution, but the copolymers of TrMA with less bulky methacrylates cannot keep their helical structure and lose their optical activity during the polymerization or after the polymerization in solution, which is highly dependent on the bulkiness of the comonomers [22]. The copolymer (19 x = 2) containing 26 mol% azobenzene units, also lost its optical activity upon irradiation within 20 min. This change is due to the helix-to-coil transition of the copolymer and can occur in the dark. 

The assigned coisotactic parameters, al2 and ct2i>were determined unequivocally by use of a totally deuterated monomer.241,242 The copolymer of MMA-t/g (Mj) with a small amount of undeuterated triphenylmethyl methacrylate (M2) was prepared in toluene by AIBN at 60°C and converted into the... 

Fig. 21. H NMR spectra of the copolymer of MMA-ds with MM A derived from the copolymer of MMA-rf8 with triphenylmethyl methacrylate normal spectrum (A), partially relaxed spectrum (B) (pulse sequence 180°-0.6s-90°-10s). (Nitrobenzene-, 110oC, 100 scans, 100 MHz.) (From Ref. 242.)...

Another differential reaction is copolymerization. An equi-molar mixture of styrene and methyl methacrylate gives copolymers of different composition depending on the initiator. The radical chains started by benzoyl peroxide are 51 % polystyrene, the cationic chains from stannic chloride or boron trifluoride etherate are 100% polystyrene, and the anionic chains from sodium or potassium are more than 99 % polymethyl methacrylate.444 The radicals attack either monomer indiscriminately, the carbanions prefer methyl methacrylate and the carbonium ions prefer styrene. As can be seen from the data of Table XIV, the reactivity of a radical varies considerably with its structure, and it is worth considering whether this variability would be enough to make a radical derived from sodium or potassium give 99 % polymethyl methacrylate.446 If so, the alkali metal intitiated polymerization would not need to be a carbanionic chain reaction. However, the polymer initiated by triphenylmethyl sodium is also about 99% polymethyl methacrylate, whereas tert-butyl peroxide and >-chlorobenzoyl peroxide give 49 to 51 % styrene in the initial polymer.445... 

---