Solvent diffusion in silica/poly[styrene‐co‐(acrylic acid)] core‐shell microspheres by pulsed field gradient NMR techniques

Abstract

Polymer‐coated SiO2 particles are prepared by precipitation of poly[styrene‐co‐(acrylic acid)] on SiO2 microspheres through an improved phase inversion method. The diffusion resistance of the polymer membrane was considered to be the critical reason for producing tailor‐made polyethylene by catalysts supported on these polymer‐coated particles. This paper employs pulsed field gradient NMR (PFG‐NMR) to distinguish diffusion of n‐hexane in different regimes, i.e., in the space between each particle, the pores in SiO2 and the polymer shell, by their respective diffusion coefficients. By varying the observation time, the time scale of the molecular exchange is discussed. A three‐region ansatz was used to interpret the exchange and diffusion in polymer‐coated SiO2 system, and was compared with results acquired with noncoated particles. At long diffusion times, the mean‐squared displacement, and thus the averaged self‐diffusion coefficient, of hexane in the system of polymer‐coated SiO2 particles is significantly reduced. The PSA membrane is identified as an efficient barrier against molecular exchange between the pores in SiO2 and the intraparticle space. Consistently, the relaxation measurements indicated that the mobility of n‐hexane molecules, especially the rotation of n‐hexane, was limited by the PSA membrane. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40160.

Valorization of lignin in polymer and composite systems for advanced engineering applications – A review

“…A few examples are presented in Table 3. lignin and switch grass as reinforcement; polymeric methylene diphenyl diisocyanate (PMDI) as compatibilizer [256] filler: acidolysis lignin and alkali enzymatic lignin [257] WAXD and SAXS investigations revealed that presence of the AL does not influence the crystal and supermolecular characteristics of the PHB [258] poly(3hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) lignin was obtained from sugar cane bagasse; lignin content up to 80% [112] starch reactive filler; lignin stabilizes the residual starch structure [259] mixed matrix: cellulose and starch; lignin filler (1-5 wt%); hybrid green composite films with excellent mechanical properties in dry and wet states, and good thermal stability and high gas barrier [260] matrix: glycerol-plasticized corn starch (GCS)adipic acid modified starch microparticles (AASM) [261] PA tall oil based polyamide [283] polybutylene adipate-ωterephtalate applications: non-food packaging or other short-lived applications (agriculture, sport) [262] PLA PEG added as plasticizer [263] three silane coupling agents: 3-aminopropyltrieethoxysilane, γ-glycidoxypropyl-trimethoxy-silane, and gmethylacryloxy-propyltrimethoxy-silane [264] composites exhibited a six-fold increase of elongation at break and a simultaneous improvement in their tensile strength and Young's modulus [265] comparative study using PP or PLA as matrix, and cellulose, lignin or wood flour as filler [266] matural rubber (NR) NR/soda lignin and NR/thiolignin composites [267] improvement of main mechanical properties [268] comparative study on natural rubber (NR) and styrene butadiene rubber (SBR) matrices; lignin filler -forming agglomerates [269] epoxidized natural rubber [270] homogeneous dispersion of filler and the strong interfacial adhesion significantly enhanced the thermal stability and mechanical properties of nanocomposites [187]…”

Applications of NMR diffusion methods with emphasis on ion pairing in inorganic chemistry: a mini‐review

“…The most popular applications involving NMR diffusion methods concern themselves with directly estimating a molecular weight (MW) frequently with the help of model compounds, as indicated in Fig. .…”

Solvents Molecular Mobility in Coked Catalyst ZSM-5 Studied by NMR Relaxation and Pulsed Field Gradient Techniques

“…Spin–lattice ( T 1 ) relaxation experiments were performed and evaluated for reactant methanol in coked catalyst samples. Signal recovery curves and fittings are shown in Figure b.…”