Free-Radical Graft Polymerization onto Starch as a Tool to Tune Properties in Relation to Potential Applications. A Review

Abstract

Abstract:Grafting of acrylic monomers onto the renewable feedstock starch via free radical polymerizations has been investigated for many years. Many potential applications have been studied, such as superabsorbents, flocculants, thickening agents and so forth. It is expected that size and spacing of the grafts have a large influence on the performance of such polymers. Yet, information upon the structure-property relationships is only scarcely found in literature. Moreover, there is no clear overview of how reaction variables can be used to influence the grafted structure. In this review, an assessment has been made of the relation between the architecture of the grafts and potential applications. Then, from a selection of relevant literature data it is demonstrated that reaction variables such as the relative concentrations of initiator and monomer, have a large impact on the average size and spacing of the grafts. The emergence of controlled radical polymerizations, like Atom Transfer Radical Polymerization (ATRP) and Reversible Addition-Fragmentation chain Transfer (RAFT), is discussed, both the current status and future prospects. These methods are promising in the future of starch grafting, especially for systems where homopolymer formation may be a problem. Nevertheless, higher costs and other related issues make these advanced methods more suitable in high added-value products.

Increasing Starch Nanoparticle Content in Emulsion Polymer Latexes

“…SNPs with particle sizes ranging from 20 nm to 6 μm can be produced through chemical pathways (e.g., reactive extrusion, emulsion precipitation) or physical treatments (e.g., microfluidization, ultrasonication). − To explore more exciting possibilities of SNP-based materials, further modification of SNPs has proven necessary. , There are generally two types of approaches to modify SNPs: via small molecule chemistry and via polymerization. Small molecule chemistry approaches are normally achieved by introducing various moieties, e.g., esters, ethers, and anhydrides. − Modification of SNPs through polymerization involves “grafting from” and “grafting to” techniques and can be performed using free radical polymerization, living/controlled radical polymerization, ring-opening polymerization, etc. ,− …”

Crosslinkable dextrin-coated latex via surfactant-free emulsion polymerization

“…However, the presence of this peak confirmed the chemical binding of a fraction of dextrins to the polymer particles. It is worth mentioning that the grafting via the abstraction of a hydroxyl hydrogen by hydroxyl radicals has been reported in the literature for the grafting of polysaccharides such as starch and cellulose [29]. The PSTY and PMMA latex particles were observed by SEM (Figure 5A) and TEM (Figure 5B,C), the other systems having a glass transition temperature (Tg) too low to prevent any deformation upon sample preparation.…”

Design and Applications of Tumor Microenvironment-Responsive Nanogels as Drug Carriers

“…Most nanogels are prepared by free radical polymerization, which have the advantages of fast reaction speed, high molecular weight of the products, and the increasing of conversion rate with the extension of reaction time (Noordergraaf et al, 2018;Gao et al, 2020). The structures and properties can be adjusted by changing monomer, crosslinking agent, initiator, reaction medium, reaction time, and reaction temperature to achieve optimal drug delivery effect (Ahmed, 2015).…”