Search results for "poros"

Effect of an organoclay on the photochemical transformations of a PBAT/PLA blend and morpho-chemical features of crosslinked networks

2021

Abstract In this work, we report the effect of an organoclay on the photochemical weathering of nanocomposites based on a poly(butylene adipate-co-terephthalate) (PBAT)/poly(lactic acid) (PLA) blend. The evolution of physicochemical properties was monitored by integrating spectroscopic, mechanical, and morphological analyses. A robust relationship was found between the molecular transformations of the polymer macromolecules and the morpho-mechanical properties of irradiated films. Moreover, the analysis of insoluble fractions extracted from nanocomposites pointed out that free-standing, porous structures, displaying an unprecedented thickness as great as 100 µm, were formed, thus unambiguou…

Simulations of Polymers in Confined Geometries

1991

The properties of flexible polymers moving inside porous structures are believed to be relevant to practical problems such as filtration, gel permeation chromatography, heterogeneous catalysis, oil recuperation, etc.1. Similarly the adsorption of macromolecules on interfaces plays an important role for problems such as adhesion, flocculation and stabilisation of colloid particles, biological membrane function, artificial organs in medicine, etc. 2. Aside from this eventual practical application, the configurational statistics of polymers in such confined geometries is a challenging problem of theoretical physics. The present brief review will be concerned with the study of a single long fle…

Mechanical behavior and structure of single beads of homogeneous and macroporous styrene–divinylbenzene copolymers

1982

The stress–stain and ultimate behavior in compression of homogeneous and macroporous beads of styrene–divinylbenzene copolymers has been investigated in the dry state or in equilibrium with toluene, acetone, methanol, and water. The penetration modulus A indicates sensitively the transition from the glassy into the rubbery state induced by an increase in temperature or swelling. For macroporous copolymers, A of the glassy polymers is mainly determined by the porosity P, while in the rubbery region it primarily depends on the matrix structure (degree of crosslinking and concentration and composition of the diluent). The high value of the slope s of the A vs. P dependence (s ∼ −3) for macropo…

Insights into the Dynamics of Grotthuss Mechanism in a Proton-Conducting Chiral bioMOF

2016

Proton conduction in solids attracts great interest, not only because of possible applications in fuel cell technologies, but also because of the main role of this process in many biological mechanisms. Metal–organic frameworks (MOFs) can exhibit exceptional proton-conduction performances, because of the large number of hydrogen-bonded water molecules embedded in their pores. However, further work remains to be done to elucidate the real conducting mechanism. Among the different MOF subfamilies, bioMOFs, which have been constructed using biomolecule derivatives as building blocks and often affording water-stable materials, emerge as valuable systems to study the transport mechanisms involve…

Biological evaluation of PLLA membranes, with different pore diameters, to stimulate cell adhesion and growth in vitro

2015

Polymeric membranes prepared via DIPS (Diffusion Induced Phase Separation) are widely studied and utilized as scaffolds for the regeneration of tissue. In this work, poly (L)-lactide membrane are prepared through a DIPS protocol starting from a ternary solution made of polymer, dioxane (solvent) and water (non-solvent). A three-dimensional, porous and mechanically stable membrane is desirable for ingrowth of human bronchial epithelial cells. Polymeric membranes prepared via DIPS (Diffusion Induced Phase Separation) are widely studied and utilized as scaffolds for the regeneration of tissue. In this work, poly (L)-lactide membrane are prepared through a DIPS protocol starting from a ternary …

An Appraisal by M.I.P of the Changes Induced in the Microstructure of Complex Sulfide Ores by Reactive Thermal Treatments in H2 and N2

1991

Summary Changes in the microstructure of complex sulfide ores resulting from reactive thermal treatments in either H2 or N2 were investigated qualitatively by combined scanning electron microscopy and X ray microanalysis, and quantitatively by mercury intrusion porosimetry (MIP) and mercury pycnometry. With increasing treatment temperature, we successively observed: 1) the development of fractures, preferentially at interfaces between the various mineral components, 2) the development of meso and macropores and the simultaneous swelling of the solids and 3) the crystallization or recrystallization of the metal or sufide phase products. In all cases the specific pore volume and mean pore dia…

Functionalization of Porous Polymers from High‐Internal‐Phase Emulsions and Their Applications

2012

The fractal calibration method applied to the characterization of polymers in solvent mixtures and in mixed gel packings by SEC.

2007

The size-exclusion chromatographic (SEC) behaviour of different solvent/polymer systems in three packing sets has been analysed from fractal considerations. The three-column sets studied are specifically formed by: (i) 'pure' micro-styragel, (ii) 'mixed' TSK Gel H(HR + XL + HR) and (iii) mixed TSK Gel H(XL + HR + XL). The experimental data reveals that in most of the systems assayed the classical universal calibration (UC) is not fulfilled, denoting the existence of secondary effects accompanying the main SEC mechanism. In order to obtain an accurate characterization of different polymers eluted in solvent mixtures and/or mixed packings, the use of a reliable and trusted calibration curve i…

Tuning of biodegradation rate of PLLA scaffolds via blending with PLA

2009

Blends of Poly-L-Lactic Acid (PLLA) with Poly-Lactic Acid (PLA) in different proportions (95/5, 90/10, 80/20, 70/30 and 60/40) were utilized in order to realize biodegradable and biocompatible scaffolds for soft tissue engineering applications. The scaffolds were produced via thermally induced phase separation (TIPS) starting from ternary systems where dioxane was the solvent and water the non-solvent. Morphology was evaluated by Scanning Electron Microscopy (average pore size and interconnection). Foams’ apparent density was also evaluated (porosity ranges from 87% to 92%). Moreover an in vitro biodegradation test of scaffolds was set-up in order to verify the rate of degradation of the va…

Super-high-speed liquid chromatography of proteins and peptides on non-porous Micra NPS-RP packings

1999

Abstract The new generation of non-porous silica RP packings commercially available from Micra Scientific was tested for separations of peptides and proteins by means of the gradient HPLC. Extremely high-speed separations were achieved using conventional chromatographic equipment: six proteins could be completely separated within six seconds. Tryptic digest peptides could be resolved in more then 40 components within 2–3 min. The effect of the experimental parameters such as temperature, flow rate etc. was investigated.