Application of amphiphilic polysaccharides as stabilizers in direct and inverse free-radical miniemulsion polymerization

Dextran-Coated Latex Nanoparticles via Photo-RAFT Mediated Polymerization Induced Self-Assembly

Polysaccharide coated nanoparticles represent a promising class of environmentally friendly latex to replace those stabilized by small toxic molecular surfactants. We report here an in situ formulation of free-surfactant core/shell nanoparticles latex consisting of dextran-based diblock amphiphilic copolymers. The synthesis of copolymers and the immediate latex formulation were performed directly in water using a photo-initiated reversible addition fragmentation chain transfer-mediated polymerization induced self-assembly strategy. A hydrophilic macromolecular chain transfer-bearing photosensitive thiocarbonylthio group (eDexCTA) was first prepared by a modification of the reducing chain end of dextran in two steps: (i) reductive amination by ethylenediamine in the presence of sodium cyanoborohydride, (ii) then introduction of CTA by amidation reaction. Latex nanoparticles were then formulated in situ by chain-extending eDexCTA using 2-hydroxypropyl methacrylate (HPMA) under 365 nm irradiation, leading to amphiphilic dextran-b-poly(2-hydroxypropyl methacrylate) diblock copolymers (DHX). Solid concentration (SC) and the average degree of polymerization - Xn-- of PHPMA block (X) were varied to investigate their impact on the size and the morphology of latex nanoparticles termed here SCDHX. Light scattering and transmission electron microscopy analysis revealed that SCDHX form exclusively spherical nano-objects. However, the size of nano-objects, ranging from 20 nm to 240 nm, increases according to PHPMA block length.

Natural biodegradable polymers based nano-formulations for drug delivery: A review

Nanomedicines are now considered as the new-generation medication in the current era mainly because of their features related to nano size. The efficacy of many drugs in their micro/macro formulations is shown to have poor bioavailability and pharmacokinetics after oral administration. To overcome this predicament, use of natural/synthetic biodegradable polymeric nanoparticles (NPs) have gained prominence in the field of nanomedicine for targeted drug delivery to improve biocompatibility, bioavailability, safety, enhanced permeability, better retention time and lower toxicity. For drug delivery, it is essential to have biodegradable nanoparticle formulations for safe and efficient transport and release of drug at the intended site. Moreover, depending on the target organ, a suitable biodegradable polymer can be selected as the drug-carrier for target specific as well as for sustained drug delivery. The aim of this review is to present the current status and scope of natural biodegradable polymers as well as some emerging polymers with special characteristics as suitable carriers for drug delivery applications. The most widely preferred preparation methods are discussed along with their characterization using different analytical techniques. Further, the review highlights significant features of methods developed using natural polymers for drug entrapment and release studies.

On the Use of Starch in Emulsion Polymerizations

The substitution of petroleum-based synthetic polymers in latex formulations with sustainable and/or bio-based sources has increasingly been a focus of both academic and industrial research. Emulsion polymerization already provides a more sustainable way to produce polymers for coatings and adhesives, because it is a water-based process. It can be made even more attractive as a green alternative with the addition of starch, a renewable material that has proven to be extremely useful as a filler, stabilizer, property modifier and macromer. This work provides a critical review of attempts to modify and incorporate various types of starch in emulsion polymerizations. This review focusses on the method of initiation, grafting mechanisms, starch feeding strategies and the characterization methods. It provides a needed guide for those looking to modify starch in an emulsion polymerization to achieve a target grafting performance or to incorporate starch in latex formulations for the replacement of synthetic polymers.

Synthesis of nanostructured materials in inverse miniemulsions and their applications

Polymeric nanogels, inorganic nanoparticles, and organic-inorganic hybrid nanoparticles can be prepared via the inverse miniemulsion technique. Hydrophilic functional cargos, such as proteins, DNA, and macromolecular fluoresceins, may be conveniently encapsulated in these nanostructured materials. In this review, the progress of inverse miniemulsions since 2000 is summarized on the basis of the types of reactions carried out in inverse miniemulsions, including conventional free radical polymerization, controlled/living radical polymerization, polycondensation, polyaddition, anionic polymerization, catalytic oxidation reaction, sol-gel process, and precipitation reaction of inorganic precursors. In addition, the applications of the nanostructured materials synthesized in inverse miniemulsions are also reviewed.

Macromolecular surfactants for miniemulsion polymerization

The use of polymeric surfactants as stabilizers in miniemulsion polymerization was reviewed. The structural characteristics of reported polymeric surfactants were detailed and compared. The concept of multi-functional polymeric surfactants was evidenced. The specificities brought by polymeric surfactants in the process of miniemulsion polymerization in comparison to molecular surfactants were analysed for the stability of the initial monomer emulsion, polymerization kinetics and characteristics of the obtained latexes. The contribution of polymeric surfactants to the control of the characteristics of the obtained nanoparticles was detailed with regard to the nature of the core material and to the surface coverage. Polymeric surfactants can be seen as powerful tools for the design of original nanoparticles. On the basis of the available data, possible research topics are suggested.