Optimized synthesis of styrenic tackifying resins

Technical pure styrene monomer was cationically polymerized either alone or with alpha -metylstyrene to prepare tackifying resins. Anhydrous aluminum chloride dispersed in toluene was used as the catalyst. The polymerization was optimized with emphasis on practical viewpoints, and incremental monome r addition method was used in all the syntheses. Certain parameters affecte d on the reaction and on the resin characteristics, i.e., starting reaction temperature, catalyst percent, monomer and comonomer concentration, and so lvent type were investigated. Post-heating of the resins was briefly studie d as well. Number average molecular weight (M-n) and polydispersity (PDI) o f the resins were determined by size-exclusion chromatography. Changes of M -n and PDI, as well as the reaction rate and yield versus variation of the mentioned parameters, were basically investigated according to the mechanis m of carbocationic polymerization. Finally, the structure of the synthesize d resins was confirmed by IR and NMR spectroscopy. A graphical method was p roposed to quantify comonomer composition of the copolymeric resins by usin g of the ratio of aromatic to aliphatic protons peak area from the correspo nding NMR spectra. (C) 2001 John Wiley & Sons, Inc.