US  10,031,416 B2  6  5  2.00 g of2,4-dimethoxy-4’-hydroxybenzophenone, 2.48 g  of 2-chioroethyl vinyl ether and 3.21 g of potassium car- bonate are dissolved in 12.0 g ofDMF. The mixture is stirred  at 110 degrees Celsius for 15 hours, after which the mixture  is cooled to 25 degrees Celsius and further stirred after  addition of 60.0 g of water and then extracted with 24.0 g  toluene and the organic phase is washed with water. There› after, toluene is distilled away, thereby obtaining 3.59 g of  2,4-dimethoxy-4’-(2-vinyloxyethoxy)-benzophenone.  3.59 g of 2,4-dimethoxy-4’-(2-vinyloxyethoxy)-benzo- phenone, 0.28 g of pyridinium p-toluenesulfonate and 2.1 g  of water are dissolved in 18.0 g of acetone. The mixture is  stirred at 35 degrees Celsius for 12 hours, after which the  mixture is further stirred after addition of 3% aqueous  solution of sodium carbonate, and then extracted with 28.0  g ethyl acetate and the organic phase is washed with water.  Thereafter, ethyl acetate is distilled away, thereby obtaining  3.04 g of 2,4-dimethoxy-4’-(2-hydroxyethoxy)-benzophe› none.  2.8 g of 2,4-dimethoxy-4’-(2-hydroxyethoxy)-benzophe› none and 1.4 g of methacrylic anhydride are dissolved in 20  g oftetrahydrofuran. 1.0 g oftriethylamine dissolved by 3.0  g of tetrahydrofuran is added dropwise to the mixture over  10 minutes and then the mixture is stirred at 25 degrees  Celsius for 3 hours. The mixture is then further stirred after  addition of water and then extracted with 28 g ethyl acetate  and the organic phase is washed with water. Thereafter, ethyl  acetate is distilled away, and the resultants are purified by  silica gel colunm chromatography (ethyl acetate:hexane=2:  8), thereby obtaining 2.96 g of 2,4-dimethoxy-4’-(2-meth- acryloxyethoxy )-benzophenone.  2.8 g of 2,4-dimethoxy-4’-(2-methacryloxyethoxy)-ben› zophenone, 0.05 g bismuth (III) trifluoromethanesulfonate  and 5.2 g oftrimethyl orthofomate are dissolved in 7.0 g of  methanol. The mixture is stirred at reflux temperature for 72  hours, after which the mixture is cooled to 25 degrees  Celsius, further stirred after addition of a 5% aqueous  NaHCO$_{3 }$ solution, and then extracted with 30 g ethyl acetate  and the organic phase is washed with water. Thereafter, ethyl  acetate is distilled away and the resultants are purified by  silica gel colunm chromatography (ethyl acetate:hexane=l:  9), thereby obtaining 1.92 g of (2,4-dimethoxyphenyl)-[4- (2-methacryloxyethoxy)-phenyl]-dimethoxymethane.  A solution containing 0.82 g of (2,4-dimethoxyphenyl)› [ 4-(2-methacryloxy-ethoxy)-phenyl]-dimetoxymethane, 3 .0  g of a-methacryloyloxy-y-butylolactone, 2.6 g of 2-methyl› adamantane-2-methacrylate, 3.1 g of 3-hydroxyadaman› tane-1-methacrylate, 0.51 g of dimethyl-2,2’-azobis(2-meth› ylpropionate) and 11.2 g oftetrahydrofuran is prepared. 0.2  g of butyl mercaptane is added to the solution because a  corresponding radical generated from butyl mercaptane dur› ing the reaction of the solution adjusts the chain length of the  polymer to be generated. The prepared solution is added  dropwise for 4 hours to 8.0 g of tetrahydrofuran placed in  flask while stirring and boiling. After the addition of the  prepared solution, the mixture is heated to reflux for 2 hours  and cooled to room temperature. Addition of the mixture by  drops to a mixed liquid containing 110 g of hexane and 11  g of tetrahydrofuran while vigorously stirring, precipitating  the copolymer. The copolymer is isolated by filtration.  Purification of the copolymer is carried out by vacuum  drying following two washings by 40 g of hexane, thereby  obtaining 6.9 g of white powder of the copolymer (Resin B).  Example 2  A solution containing 5.0 g of a-methacryloyloxy-y- butylolactone, 6.03 g of 2-methyladamantane-2-methacry- late, and 4.34 g of 3-hydroxyadamantane-1-methacrylate,  0.51 g of dimethyl-2,2’-azobis(2-methylpropionate )3-hydro- cyadamantane-1-methacrylate, and 26.1 g of tetrahydro› furan is prepared. The prepared solution is added for 4 hours  to 20.0 g of tetrahydrofuran placed in a flask while stirring  and boiling. After the addition of the prepared solution, the  mixture is heated to reflux for 2 hours and cooled to room  temperature. Addition of the mixture by drops to a mixed  liquid containing 160 g of hexane and 18 g of tetrahydro› furan while vigorously stirring, precipitating the copolymer.  The copolymer is isolated by filtration. Purification of the  copolymer is carried out by vacuum drying following two  washings by 70 g ofhexane, thereby obtaining 8.5 g of white  powder of the copolymer.  Resin A  (3)  (4)  Synthesis of 2,4-dimethoxy-4’-(2-vinyloxyethoxy)› benzophenone  Synthesis of 2,4-dimethoxy-4’-(2-hydroxyethoxy)› benzophenone  Synthesis of 2,4-dimethoxy-4’-(2-methacryloxy› ethoxy )-benzophenone  Synthesis of (2,4-dimethoxyphenyl)-[ 4-(2-methacry› loxyethoxy ]-phenyl]-dimethoxymethane (Example  2) 