Nitroxide mediated polymerization of n-butyl acrylate using accelerating agents

• Myriam Gregorio De Las Heras Universidad del Zulia-Venezuela
• David León Universidad del Zulia-Venezuela
• Orietta León Universidad del Zulia-Venezuela
• Diana Soto Universidad del Zulia-Venezuela
• Haydee Oliva Universidad del Zulia-Venezuela

Resumen

The effect of the Dicumyl Peroxide (DCP), Acetol and Acetic Anhydride on the conversion evolution, and molecular weight distribution in bulk nitroxide mediated polymerizations of n-butyl acrylate (BA) was studied. Temperature profile was 1 h at 90°C, and variable reaction times (between 2 and 32 hours) at 135°C. Benzoyl peroxide (BPO) and 4-hidroxy-2,2,6,6-tetramethylpiperidinyl-1-oxyl (4-OH-TEMPO) were used as initiator and stable radical, respectively. Thermal, conventional, and nitroxide mediated polymerizations of the acrylic monomer were carried out for comparison purposes. Conversion was determined gravimetrically and some samples were selected for characterization by size exclusion chromatography (SEC). With DCP conversions were low and the polymerization was uncontrolled. Polymerization was inhibited for molar relation [DCP]/[4-OH-TEMPO] be low of 0,5; independently of the [4-OHTEMPO]/[BPO]. With acetol, reaction rate in creased respect to the polymerization with out this agent. Conversions reached 66%, while the products showed relatively narrow molecular weight distributions (PD 1,35-2,01). The polymerization rate in creased significantly at [Anh Ac]/[4-OH-TEMPO] ³ 4. In these cases, conversions were higher than 70% at first 2 h of reaction time. How ever, there was no control over these polymerizations. From the comparison of the effect for the studied agents, is possible to conclude that acetol produce better results on distribution of molar mass control, at acceptable polymer yields.