Reactive processing of polymers: Effect of bifunctional and tri-functional comonomers on melt grafting of glycidyl methacrylate onto polypropylene (2023)

N-vinyl pyrrolidone (NVP)-assisted free radical functionalization of glycidyl methacrylate (GMA) onto styrene-b-(ethylene-co-butylene)-b-styrene (SEBS) was investigated to attempt to overcome the low grafting reactivity of GMA and the low efficiency of the styrene (St)-assisted functionalization method. By using the optimal amount of NVP, the degree of GMA grafting was increased by at least 7.5 and 2.5-fold when compared to GMA alone and the St-assisted grafting procedure, respectively. Also, no apparent cross-linking or degradation reactions of SEBS were observed. It was proposed that NVP reacted first with SEBS macroradicals, and then the resulting NVP-macroradicals copolymerized with GMA to produce high degrees of grafting of both GMA and NVP onto SEBS.

Materials Letters, Volume 141, 2015, pp. 157-160

Highly ordered arrays of polyamide 6 (PA6) nanotubes were successfully prepared using photolithography via polymer solution wetting the anodic aluminum oxide (AAO) templates. The samples were examined by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD). The crystal structure and the crystallinity of the samples were influenced by the presence of nanopores in the AAO template. Nanopore-induced crystal transformation from the α-form to the γ-form of PA6 was confirmed by XRD, and the formation of γ-form crystal was enhanced by the presence of nanopores in the AAO template. The formation of γ-form crystal was also discussed. These results indicated that nanopores provided favorable conditions for the crystallization of γ phase.

Journal of Organometallic Chemistry, Volume 798, Part 2, 2015, pp. 311-316

This paper summarizes our research in the preparation of isotactic polypropylene (PP) nanocomposites containing exfoliated graphite oxide (GO) using in situ polymerization technique with Ziegler–Natta catalyst intercalated in GO. Intercalation of Ziegler–Natta catalyst in GO was conducted by treating GO with a Grignard reagent of n-BuMgCl, resulting in anchoring of -Mg-Cl species on individual GO sheets. Successive treating -Mg-Cl-intercalated GO with TiCl₄ rendered the generation of structurally simple yet highly effective Ziegler–Natta catalyst species on the substrate of GO sheets, which initiated with a high efficiency iso-specific propylene polymerization, affording nanocomposites of PP containing well-dispersed GO sheets. Further studies on the treatment of GO with n-BuMgCl revealed that with an excess amount of the Grignard reagent GO would be largely removed of its functional groups amidst -Mg-Cl species anchoring, which led to the formation of reduced GO (rGO)-intercalated Ziegler–Natta catalyst. Efficient propylene polymerization inside the rGO in turn prompted the dispersion of electrically conductive rGO sheets in the matrix of PP, the nanocomposites of which were discovered with rather high electrical conductivities with a low percolation threshold (∼0.2 vol.%).

Journal of Crystal Growth, Volume 517, 2019, pp. 68-71

Kinetics of autoepitaxial crystal growth in amorphous films of Cr₂O₃ were studied by the methods of transmission electron microscopy “in situ” with video registration of structural changes. With frame-by-frame analysis of the video, the kinetic curves of the time dependence of the radius, length and width of growing crystals with different morphological types (needle-shaped and disc-shaped crystals) were obtained. The time dependence of fraction of the crystallized material was determined. Crystallization front may be splitting into slices that can move at different speed. The conclusion was made that the autoepitaxial crystal growth is the type of layer polymorphous crystallization of amorphous films.

Progress in Organic Coatings, Volume 76, Issue 12, 2013, pp. 1786-1791

Polymer coatings with periodic topographic patterns, repeating over millimetre length scales, can be created from lateral flows in an aqueous dispersion of colloidal particles. The flow is driven by differences in evaporation rate across the wet film surface created by IR radiative heating through a shadow mask. This new process, which we call IR radiation-assisted evaporative lithography (IRAEL), combines IR particle sintering with the concept of evaporative lithography. Here, a series of experiments has been conducted in which the mass of the latex is measured as a function of the exposure time under infrared radiation through a mask. The water evaporation rates and the minimum exposure time required for a dry film are estimated as a function of the power density of the IR emitter. The temperature of the wet film is monitored to avoid overheating and boiling of the water, which will otherwise cause defects. It is demonstrated that textured films can be created on a variety of substrates (plastics, metals, paper and glass), and processing times can be as short as 5min. We use IRAEL to decorate household goods with an aesthetic coating with the desired texture.

Polymer, Volume 55, Issue 4, 2014, pp. 1012-1019

SiO₂ nanoparticles grafted to terminally hydroxylated polypropylene (PP-g-SiO₂) with different molecular weights were melt mixed with PP to prepare a series of PP/PP-g-SiO₂ nanocomposites. PP/PP-g-SiO₂ offered several advantages over pristine PP and PP/unmodified SiO₂ such as highly uniform dispersion up to 10wt.-%,+200–400% faster crystallization and+30% increments for both the Young's modulus and the tensile strength without largely sacrificing the melt viscosity of PP. We concluded that grafted chains act as crystallization nuclei and co-crystallize with matrix chains to make PP-g-SiO₂ nanoparticles as a physical cross-linker between lamellae, while the linkage disappears in melt and grafted chains minimize the cohesive attraction between nanoparticles.

Methods, Volume 64, Issue 3, 2013, pp. 183-184