Synthesis of novel alkyl alfa-(hydroxymethyl)acrylate (RHMA) ether dimer derived polymers and their potential use in powder coating

Abstract

One of the newest and most effective technologies in coating industry is powder coating. Powder coating has been applied from wood to steel surfaces. Among many components, resin has the highest percentage in the mixture which determines the characteristics of a powder coating. Some of the significant characteristics are stability, reactivity and processability. One of the physical properties that affect the most the quality of a coating and also its manufacturing process is the Tg of the resin. The lowest Tg that is possible is around 55-60 0C for a powder coating that is to be cured at 120-150oC. This Tg interval can be reached by aliphatic polyesters only at relatively high molecular weights (10,000-20,000 g/mol) which lowers the crosslink density. Decreasing molecular weight but keeping the high Tg can be achieved with aliphatic cyclopolymers. Previously in our research group, it has been shown that these Tg can be obtained at about 3000-6000 g/mol molecular weights using the cyclopolymers. Aliphatic cyclopolymers derived from tert-butyl {460}-(hydroxymethyl)acrylate dimer(TBHMA) were synthesized via atom transfer radical polymerization (ATRP) to be used as potential base resins for powder coating applications. Solution polymerizations was performed in xylene using Cu(I)Br/PMDETA as the active catalyst complex. Since the Tg requirement has been successfully fulfilled previously in our research group, for the cylpolymers to be used in powder coating application reactive end groups must be introduced to the terminal positions of the polymer. To modify end groups, two strategies were chosen. First one was the addition of alcohol or acid functionality via the addition of alcohols and acids with terminal double bonds (non-polymerizable) under ATRP conditions. Second was to employ the click chemistry. The quantitative determination of the acid and alcohol end groups was challenging and new to the literature, and this quantitative analysis was crucial since the stoichiometric ratios of the polymers and crosslinkers have to be adjusted to obtain a good coating. Cross-linking and preliminary perspective were also investigated.