Molecular structure of high molecular weight acetal resins

Abstract

Stable, high molecular weight polymers of formaldehyde have been studied to determine their molecular structure. The polymer chain was shown to be a polyoxymethylene by chemical analysis and infrared absorption spectra. Infrared techniques also revealed hydroxyl end groups which were replaced by acetate groups on esterification. The endgroups, which were also measured by chemical methods, were used to determine the number‐average molecular weight over the range 20,000 to 98,000. Values obtained by assuming two endgroups per molecule agreed with osmotic pressure results, thus showing this to be an essentially unbranched polymer. Two theoretically possible branch‐point structures were investigated by chemical methods; none could be detected, further indicating a linear polymer structure. Indirect evidence of narrow molecular weight distribution was obtained by comparing melt viscosity properties with those of other polymers of known wide and narrow distribution.

Synthesis of copolymer from 1,3,5‐trioxane and 1,3‐dioxolane catalyzed by Maghnite‐H+

“…However, there is a newly discovered mechanism for the copolymerization of TOX and DOX, using BF 3 O(Et) 2 as catalyst in the presence of nanosilica, the copolymerization give a polymer with two or more consecutive DOX units in an oxymethylene main-chain sequence, 37 which differ from the previous results of Yamasaki. 38 However, the macromolecular chain of acetal/silica nanocomposite had only one DOX unit in an oxymethylene mainchain.…”

“…Various investigators have presented two methods for determining the comonomer content: gas chromatography 29,30 and NMR spectroscopy. [31][32][33] The ring-opening copolymerization of TOX can be initiated by Lewis acid such as BF 3 O(Et) 2 , TiCl 4,34 and CH 3 COClO 4 . 35 Penczek and coworkers 36 studied the solution copolymerization of TOX and a small amount of DOX initiated by BF 3 O(n-Bu) 2 and found that the unstable fraction content of the copolymer increased with increasing conversion, indicative of a higher reactivity of DOX than that of TOX toward the copolymerization.…”

“…There are two routes for the production of polyacetal resin. One route is the polymerization of formaldehyde (acetal homopolymer), [1][2][3][4][5][6] and the other method is copolymerization of trioxane with cyclic ethers or acetals (acetal copolymer), preferably with 1,3-dioxolane [7][8][9][10] or ethylene oxide. [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28] The copolymerization of trioxane is of considerable industrial importance, because the acetal copolymer has better thermal properties and superior resistance to alkali than homopolymer and it is a commercially useful engineering plastic.…”

Thermally stable high molecular weight polyoxymethylenes

“…Molecular weights of the polymers may be measured in dimethylformamide as described in a companion paper. 14 Comparisons by the thermal stability tests show the polymers prepared in these investigations to be more stable than those obtained by procedures in the literature. Results are summarized in Table 111.…”

Polyoxymethylenes

“…IR-spectroscopic methods have been described for the determination of terminal groups in acetylated homopolymers [144,145].…”