Novel starch-g-copolymers obtained using acrylate monomers prepared from two geometric isomers of terpene alcohol

Abstract

The paper presents the studies on the optimization of the free-radical graft reaction applying the “grafting from” method of terpene acrylate monomers prepared from two geometric isomers of terpene alcohol such as trans-3,7-dimethyl-2,6-octadien-1-ol (geraniol) and cis-3,7-dimethyl-2,6-octadien-1-ol (nerol) with potato starch and the evaluation of some physico-chemical properties of the obtained materials. Based on the overall conversion (%TC) values, it was confirmed higher reactivity of neryl acrylate than geranyl acrylate in the grafting process with starch. The maximum of the grafting percent (%G) was found to be 42.8% ± 0.4 for neryl acrylate using 2 w% of an initiator, starch to monomer ratio 1:1 and the reaction time 180 min. However, the maximum of the %G for geranyl acrylate was 35.6 ± 0.4 for 2.5 wt% of an initiator, starch to monomer ratio 1:1.5 during 210 min. ATR-FTIR and 13C CP/MAS NMR analyses affirmed the structure of novel, amphiphilic graft copolymers. SEM confirmed the creation of the materials with irregular but different morphology. Generally, starch-g-poly(geranyl acrylate) copolymer (%G 35.6 ± 0.4) was characterized by lower moisture absorption, lower swelling in polar and non-polar solvents, higher chemical resistance towards less alkaline, acidic and neutral conditions, higher glass transition temperature (Tg) than starch-g-poly(neryl acrylate) copolymers (%G 35.3 ± 0.2 and 42.8% ± 0.4). As it was proved the differences in some physico-chemical properties between those two types of the copolymers were due to their structure. However, both types of the copolymers exhibited a comparable thermal stability as it was affirmed by the TG studies. Moreover, according to the TG/FTIR results, similar gaseous products were created under the heating of the studied copolymers which was due to their comparable chemical structures.