The copolymer composed of methyl methacrylate and methacrylic acid is, in contrast to pure PMMA products, able to form a 6-ring during thermal loading. In this case, 2 methacrylic acid groups have to be arranged adjacent to each other in the polymer chain (see large structural formula left), which statistically occurs with sufficiently high frequency at a mixing ratio of 2 : 1 (see molecular formula top right).

The reaction is possible at this temperature, since the water which is produced during the reaction is a very good leaving group.

The 6-ring which is formed breaks apart more easily during irradiation with electrons than the aliphatic chain re- mainder which causes the higher sensitivity of the copolymer. Once adjusted, the sensitivity will remain unchanged. The reverse ring-opening reaction is impossible.

不同於的PMMA反應機制,AR-P 617共聚物(甲基丙烯酸甲酯與甲基丙烯酸)可在軟烤溫度下形成6環結構. 在分子鏈中必需有兩個相鄰的甲基丙烯酸才能形成6環的結構(如上左圖). 統計分析, MMA與MA比例約2:1最適合. (如上右圖).

水是在此溫度下產生的離去基團.

此共聚物阻劑有較高的敏感度主要來自於分子鏈中的6環比起脂肪鏈更易於電子束下斷鍵. 因不會有反向的開環聚合反應,參數調整確定後,阻劑敏感度可維持穩定.