Poly[3,3‐bis(hydroxymethyl) oxetane]—an analog of cellulose: Synthesis, characterization, and properties

Poly[3,3‐bis(hydroxymethyl)oxetane], PBHMO, was prepared in high molecular weight (η inh up to 5.2) by polymerizing the trimethylsilylether of 3,3‐bis(hydroxymethyl)oxetane with the i ‐Bu 3 Al–0.7 H 2 O cationic catalyst at low temperature, followed by hydrolysis. PBHMO is crystalline, very high melting (314°C) and highly insoluble, much like its analog, cellulose. It is soluble in 75% H 2 SO 4 at 30°C, being 65% converted to the acid sulfate ester; these conditions are useful for viscosity measurement, since the degradation rate is low and at least an order of magnitude less than for cellulose in this solvent. PBHMO can be prepared as oriented films and fibers using the lower melting diacetate (184°C) which can be melt or solution (CHCl 3 ) fabricated and then the oriented forms saponified to oriented PBHMO. BHMO can be directly polymerized to low molecular weight, perhaps somewhat branched, PBHMO (η inh 0.1) with trifluoromethanesulfonic acid catalyst at room temperature. Poly(3‐methyl‐3‐hydroxymethyloxetane), (PMHMO), prepared in high molecular weight (η inh up to 3.8) by the same method used for PBHMO, is more soluble and lower melting (165°C) than PBHMO, appears to be atactic and can be compression molded at 195°C to a tough, clear film which is readily oriented. Copolymers of BHMO with MHMO are crystalline over the entire composition range with a linear variation of T m with composition, a new example of isomorphism in the polymer area.