THE SYNTHESIS AND CHARACTERIZATION OF BLOCK COPOLYMERS

Segmented (AB) $\sb{n}$ polyurethanes. A series of polyether-polyurethane (PEPU) were synthesized and characterized. Soft segments were poly(propylene oxide) (PPO; M$\sb{\rm n}$ = 2,000) or poly(tetrahydrofuran) (PTHF; M$\sb{\rm n}$ = 1,650). Hard segments were formed from 4,4$\sp\prime$-diphenylmethanediisocyanate (MDI) and different short chain diols as chain extenders. In the PPO series 1,5-pentandiol (P), diethylene glycol (D), triethylene glycol (T) and 1,3-bis(N,N $\sp\prime$-methyl- N,N $\sp\prime$-2-hydroxyethyl)isophthalamide (Bi(M)) were used as chain extenders. In the PTHF series 1,6-bis(N,N $\sp\prime$-2-hydroxyethyl)adipamide (A), Bi(M), D, T, bis(N,N $\sp\prime$-hydroxyethyl)isophthalamide (Bi) and 1,6-bis(N,N $\sp\prime$-methyl- N,N $\sp\prime$-2-hydroxyethyl)adipamide (A(M)) were used as chain extenders. Degree of phase separation was investigated by IR and low temperature DSC. In the PPO-based series, P- and D-extended PEPU polymers have higher degrees of phase separation than T-extended PEPU polymers. In the PTHF-based series, the relative degree of phase separation decreases in following order, A- $\u3e$ D- $\u3e$ T-extended polymers. In either PPO- and PTHF-based series, Bi(M)-extended PEPU copolymers are phase-separated but with disordered or amorphous hard domain. Styrene-THF-Styrene Triblock copolymer. A-B-A triblock copolymer with A block as polystyrene and B block as PTHF was synthesized and characterized. IR, GPC and simple visual observation demonstrated the effectiveness of this coupling processes. $\sp{1}$H NMR analysis revealed a styrene content of 50% by weight. Also, this triblock copolymer did not flow below 125$\sp\circ$C. Acid-catalyzed decomposition of polyether, polyacetal and urethane copolymers. PTHF and poly(1,3-dioxepane) (PDXP) in addition to their acetate- and phenyl isocyanate-capped derivatives as well as PTHF-based PEPU\u27s were the subjects of TGA studies. Ethyl 2-naphthalenesulfonate (ET-NS) was used as acid-generator to catalyze polymer decomposition. Homopolymers PTHF, PDXP, acetate-capped PTHF and PDXP showed enhanced decomposition in the presence of ET-NS as compared with thermal decomposition. End-capping improved stability towards thermal and acid-catalyzed decomposition. PEPUs synthesized from amide type chain-extenders such as A and Bi(M) exhibited no acid-catalyzed decomposition. This contrasts with PEPU copolymers synthesized from D and T chain-extenders, in which acid-catalyzed decomposition was observed. The possible role of amide linkages in PEPU as base is proposed