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SYNOPSISUnsaturated polyacetals have been prepared by anionic copolymerization of acrolein with aldehydes, such as, acetaldehyde, propionaldehyde, isobutylaldehyde, pivaldehyde, and benzaldehyde. The new copolymers have essentially an acetal structure as the result of the acrolein preference to copolymerize through the carbonyl group when alcaline cyanides are used as catalysts. The influence of temperature, nature of the aldehyde and monomer composition on the molecular size, polymerization rate, and composition and structure of the copolymer are studied. These copolymers undergo cross-linking when exposed simultaneously to oxygen and light. The variables affecting the oxidation process and the products obtained were studied.In a previous paper1 we explained the exploratory study carried out on copolymerization of acrolein with aldehydes, using sodium cyanide as catalyst. Unsaturated copolyacetals were prepared with acetaldehyde, propionaldehyde, pivaldehyde, and benzaldehyde and the structure of acrolein-aldehyde copolymers was determined by NMR and IR spectroscopy.In the present work, the influence of temperature, nature of the aldehyde and monomer composition on the molecular size, polymerization rate, and composition and structure of the copolymers are studied ; auto-oxidation of prepared unsaturated polyacetals and their transformation into cross-linking substances has also been object of study. EXPERIMENTAL Monomers and solvents.Acrolein and the solvents used were purified following the methods described in previous works.2J Acid impurities present in aldehydes were eliminated by treatment with monohydrate sodium carbonate for 24 hr. The aldehydes were filtered and rectified in a column filled with Fenske rings under extremely pure nitrogen before use. Purity controls were made by gas chromatography. 311 LAPENA, MATEO, AND SASTRECatalyst. Saturated solutions of NaCN in DMF were prepared from pure NaCN that was maintained on P205 and high vacuum for 12 hr. Fresh solutions were prepared every week.Copolymerization technique. The process used was described in detail in a previous work.5 All the components were transferred to the reaction vessel using a high vacuum line. The reaction vessel was then pressurized with pure nitrogen and cooled to the desired temperature. Catalyst solution was injected by means of a hypodermic syringe through a serum cap.Characterization. KBr pellets of known concentrations were used to record the IR spectra (Perkin-Elmer Infracord 137E, 257 and 457). The NMR spectra were recorded from solutions of polymer in ClsCD, using TMS as a reference substance (Perkin-Elmer Model R-12). Copolymer composition was estimated by measuring the area under the NMR peaks.Molecular weight was determined on a Hitachi-Perkin-Elmer 115 (vapor pressure osmometry) in ClsCH solutions.The gas chromatography-mass spectrometric technique was used for analysis of oxidation liquid products (Perkin-Elmer, model 270).