Abstract
The presented work aimed to test influence of poly(L-lactide-co-glycolide)-block-poly (ethylene oxide) copolymer modification by blending with grafted dextrin or maltodextrin on the course of degradation in soil and the usefulness of such material as a matrix in the controlled release of herbicides. The modification should be to obtain homogenous blends with better susceptibility to enzymatic degradation. Among all tested blends, which were proposed as a carrier for potential use in the controlled release of plant protection agents, PLGA-block-PEG copolymer blended with grafted dextrin yielded very promising results for their future applications, and what is very importantly proposed formulations provide herbicides in unchanged form into soil within few months of release. The modification PLAGA/PEG copolymer by blending with modificated dextrins affects the improvement of the release profile. The weekly release rates for both selected herbicides (metazachlor and pendimethalin) were constant for a period of 12 weeks. Enzymatic degradation of modified dextrin combined with leaching of the degradation products into medium caused significant erosion of the polymer matrix, thereby leading to acceleration of water diffusion into the polymer matrix and allowing for easier leaching of herbicides outside the matrix.
Highlights
Conventional formulations of agrochemicals can contaminate the environment, in particular for intensive cropping
We previously investigated a blocked terpolymer with a chain composed of two blocks, namely L-lactide/glycolide copolymer block and polyethylene glycol (PEG) block [23], where we demonstrated the effect of comparatively small content of PEG blocks on strong acceleration of degradation in activated sludge or in soil
Among all the tested blends, which were proposed as a carrier for potential use in controlled release of plant protection agents, PLGA-block-PEG copolymer blended with grafted dextrin yielded very promising results for their future applications
Summary
Conventional formulations of agrochemicals can contaminate the environment, in particular for intensive cropping. There is a need for controlled release formulations of agrochemicals such as polysaccharides to reduce pollution and health hazards. Natural polymers are gaining considerable acceptance over synthetic polymers as controlled-release devices because of their eco-friendly nature, cost-effectiveness, easy availability, and biodegradability [1,2]. Biodegradability of starch has attracted attention in scientific and industrial fields, and it has many uses. Raw starch has some defects that limit its industrial applications; modifications are needed. Grafting is an important technique for modifying the properties of polymers. Chemical modification of starch by graft copolymerization makes starch and synthetic polymer bind together rather than exist merely as a physical mixture. Synthetic monomers and polymers were used to modify the properties of raw starch, and semi-synthetic polymers were obtained, thereby increasing application areas and attracting the attention of researchers [3]. Graft copolymerization provides a tool for researchers to Materials 2020, 13, 832; doi:10.3390/ma13040832 www.mdpi.com/journal/materials
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