本研究合成出具兩種不同硬鏈節氨基甲酸酯鏈段（urethane）的矽氧烷-氨基甲酸酯共聚合體（Si-PU），一為由4,4'-二苯引基二異氰酸鹽（MDI）與1,4-丁二醇（1,4-BD）所組成的urethane 1鏈段；另一為由MDI與末端為羥基的聚二甲基矽氧烷（PDMS）所組成的urethane 2鏈段，TGA測試與Ozawa方法均證實此兩種urethane鏈段的衰解階段不同，在微分衰解曲線（DTG）上顯示此兩種urethane鏈段最大衰解溫度分別在300℃與340℃附近，而其衰解活化能分別在101~117 kj/mol與130~160 kj/mol。Si-PU的軟鏈節由聚二甲基矽氧烷（PDMS）所組成，其衰解溫度高於硬鏈節，最大衰解溫度發生在480℃附近，衰解產物為環狀矽化物，而且在高溫下環狀矽化物會形成巨分子環狀物。TG/DTG測試與Ozawa方法均顯示Si-PU的衰解是不同於傳統聚氨基甲酸酯的兩衰解階段，尤其是在urethane鏈段上出現兩個不同的衰解階段。而由緩慢的升溫速度下（1℃/min）所得TG/DTG曲線證實PsiU共聚合體總具有四個衰解階段。

　　　　　Siloxane urethane copolymers (Si-PU) with two types of urethane hard segments (urethanel and urethane2) were synthesized by one step process. Urethanel consisted of 4,4'-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (1,4-BD). Urethane2 consisted of MDI and OH-terminated polydimethylsiloxane (PDMS). The characteristics of degradation in the urethane hard segments demonstrated by TGA analysis and Ozawa method presented two types of temperature. The maximum temperature and activation energy of urethanel were around 300℃ and 101~117 kJ/mol, respectively, and those of urethane2 were around 340℃ and 130~160 kJ/mol. The degradation temperature of PDMS soft segment was higher than hard segment and the maximum temperature occurred at 480℃. Furthermore, a cyclosiloxane of decomposition produced resulted from thermal decomposition of PDMS at the temperature, and subsequently produced macrocyclics beyond 480℃. The degradation of SiPU was differed from the typical two stages of degradation of conventional polyurethane. Particularly, urethane segments of SiPU possessed two types of degradation. Moreover, the TG/DTG surves which obtained from low heating rate (1℃/min) confirmed those copolymers had four stages of degradation.