Chemical functionalization of nano fibrillated cellulose by glycidyl silane coupling agents: A grafted silane network characterization study.

Nano fibrillated cellulose (NFC) has turned into a material widely studied due to its desirable performance for numerous organic systems. Nevertheless, its surface is not very compatible with most organic systems; hence, chemical functionalization methods offer a path to solve this problem. In this study, NFC is successfully functionalized with two silane coupling agents: 3-glycidyloxypropyl trimethoxysilane (GPS) and 3-glycidyloxypropyl dimethylethoxysilane (GPMES) by a simple, direct, and environmentally friendly method. Different analyses have been carried out in order to confirm the chemical modification of NFC. ATR-IR, XPS, and 29Si NMR spectroscopies confirmed the chemical modification that allowed the understanding of the structure and the conformation onto the modified NFC surface. SEM and AFM microscopies were performed to study possible alterations in morphology; a slight change was observed. Thermal properties were also analyzed by TGA analysis. It remains stable after chemical functionalization. Grafted NFC showed good performance compared to the pristine one. It allows a better dispersion into organic systems improving their properties.

Graphene Oxide-Induced Interfacial Transcrystallization of Single-Fiber Milkweed/Polycaprolactone/Polyvinylchloride Composites.

Understanding the interfacial crystallization is crucial for semi-crystalline polymer/natural fiber composites because it links to the final properties. This work reports, for the first time, the interfacial crystallization of a miscible blend between polycaprolactone (PCL) and polyvinylchloride (PVC) with milkweed fibers. We have first described the morphology of the fibers and the chemical composition of waxes covered on its surface. Our findings show that the transcrystallization (TC) layer of PCL/PVC could appear at the interface by simply coating with a layer of graphene oxide (GO) on the milkweed fiber. In our study, atomic force microscopy-infrared spectroscopy analysis shows that the crystallinity of the blends is higher at the vicinity of the interface compared to that in the bulk. The kinetic of the interfacial crystallization in terms of spherulite morphology and crystal growth rates at the nanoscale is examined. X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy were used to analyze the prepared GO and evaluate its relationship with the interfacial crystallization behavior of the blends.

Recent Applications of Advanced Atomic Force Microscopy in Polymer Science: A Review.

Atomic force microscopy (AFM) has been extensively used for the nanoscale characterization of polymeric materials. The coupling of AFM with infrared spectroscope (AFM-IR) provides another advantage to the chemical analyses and thus helps to shed light upon the study of polymers. This paper reviews some recent progress in the application of AFM and AFM-IR in polymer science. We describe the principle of AFM-IR and the recent improvements to enhance its resolution. We also discuss the latest progress in the use of AFM-IR as a super-resolution correlated scanned-probe infrared spectroscopy for the chemical characterization of polymer materials dealing with polymer composites, polymer blends, multilayers, and biopolymers. To highlight the advantages of AFM-IR, we report several results in studying the crystallization of both miscible and immiscible blends as well as polymer aging. Finally, we demonstrate how this novel technique can be used to determine phase separation, spherulitic structure, and crystallization mechanisms at nanoscales, which has never been achieved before. The review also discusses future trends in the use of AFM-IR in polymer materials, especially in polymer thin film investigation.

Sub-micronic capsules based on gelatin and poly(maleic anhydride-alt-vinyl acetate) obtained by interfacial condensation with potential biomedical applications.

New sub-micronic capsules based on a copolymer of maleic anhydride-alt-vinyl acetate and a natural polymer (gelatin) using an interfacial condensation method were obtained. Sub-micronic capsules were characterized by Fourier Transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) method, zeta-potential, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The thermal properties were investigated by thermogravimetric analysis (TGA). According to some parameters of the synthesis reaction (polymer weight ratio, acetone/water ratio, surfactant concentration), the mean diameter of the sub-micronic capsules can be tuned from 200 to 760 nm. The sub-micronic capsules show a higher agglomeration tendency as the amount of gelatin in their composition increases. The swelling capacity in aqueous solutions is dependent on the composition and size of the sub-micronic capsules, decreasing with their diameter and gelatin composition. The drug loading and release capacity was studied using Penicillin G (sodium salt) (PG), and it has been proved that it is influenced by the sub-micronic capsules morphology induced by preparation parameters. Encapsulation and controlled release of small molecule were successfully carried out, demonstrating the potential biomedical applications of these new easily obtained sub-micronic capsules.

Rheological properties of silica dispersions stabilized by stereoregular poly(methyl methacrylate).

The adsorption of stereoregular polymers and its effect on the conformation and dynamics of the polymer at interfaces are only poorly understood. 1H NMR has revealed a lowering of the peaks assigned to isotactic sequences whatever the PMMA tacticity, which provides evidence of stereospecific adsorption of the isotactic segments on silica. Entropic factors are therefore assumed to control the configuration of the adsorbed layer. Tacticity-dependent rheological behavior is revealed by dynamic investigations carried out on silica dispersions. The driving forces likely to induce the stereoselective adsorption and tacticity-dependent rheology of suspensions are discussed.