High temperature synthesis of vinyl terminated polymers based on dendronized acrylates: a detailed product analysis study

The combination of dendrons and high temperature acrylate polymerization represents a viable route to form dendronized macromonomers. Dendronized acrylates based on 2,2-bis(hydroxymethyl)propionic acid (bis-MPA) were synthesized using dendrimer synthesis and click chemistry (copper catalyzed azide alkyne cycloaddition (CuAAC)). The synthesis was carried out up to the 3rd generation and with a carbon spacer length of 6 or 9 between the acrylic function and the dendron core. These dendronized acrylates were subjected to auto-initiated high temperature acrylate polymerization. The polymerization was performed at 140 °C in a 5 wt% solution of hexyl acetate with a 2,2'-azobis(isobutyronitrile) (AIBN) concentration of 5 x 10-3 g mol-1. The vinyl terminated polymers were in-depth characterized via size exclusion chromatography (SEC) and size exclusion chromatography coupled to electrospray ionization mass spectrometry (SEC-ESI-MS) to assess the generated product spectrum and the efficiency of the process. The achievable number average molecular weight, Mn, was between 1700 and 4400 g mol -1. The degree of polymerization, DPn, decreases with increasing generations of the dendronized acrylates from 6.3 to 3.4. The purity of vinyl terminated oligomers containing a geminal double bond is up to 83%, with the dendronized acrylates of the 1st generation providing the best result. Moderate deprotection of the acetonide groups occurred spontaneously during the macromonomer formation process and reached its maximum at generation 3. © The Royal Society of Chemistry 2011.