Critical points in the formulation of pharmaceutical swellable controlled release dosage forms——Influence of particle size

Swellable matrix represents one of the most employed controlled release systems. These dosage forms provide slow release of drugs to reduce the fluctuation of drug concentration in plasma in order to improve the efficiency of treatment and/or to reduce adverse effects. The application of the concepts of statistical physics has allowed discovering the existence of critical points in the formulation of swellable matrices. These points, representing the volume fractions of the tablet components where the properties of the matrix diverge or change suddenly, provide important knowledge of how to rationalize the design of swellable matrices. The critical points are generally related to the percolation threshold of one of the components of the formulation, which corresponds to a geometrical phase transition of this component, passing from isolation to spanning the whole system. The last section of the paper is devoted to more recent findings concerning the influence of particle size of the components on the percolation threshold of the matrix forming polymer, and therefore on the release behaviour of the matrix. Knowledge of the excipient percolation threshold allows a more rational design of swellable matrices, according to the guidelines of the regulatory authorities concerning science-based formulation and quality by design.

Reversely Swellable Porphyrin-linked Microporous Polyimide Networks with Super-adsorption for Volatile Organic Compounds

A series of microporous polyimide networks with porphyrin units （Pr-MPIs） were facilely synthesized through a one-step solution polymerization process. Of particular interest is that Pr-MPI-1 containing distorted spirobisindane unit revealed the highest BET surface area （953 m^2/g）, total pore volume （0.75 cma/g）, and extreme hysteresis between the N2 adsorption and desorption isotherm. Further study revealed the prepared Pr-MPI-1 exhibited a synergistic structural effect on exceptional uptake of volatile organic compounds （VOCs） due to the high porosity and highly distorted spirobisindane structure enabled large interface and the swellability. This new approach would open up a facile approach toward the preparation of highly swellable high performance polymeric microporous materials, which are deeply wanted for environment-related applications such as VOCs adsorption and oil/water separation.

Effect of Cr2O3 addition on oxidation induration and reduction swelling behavior of chromium-bearing vanadium titanomagnetite pellets with simulated coke oven gas

The oxidation induration and reduction swelling behavior of chromium-bearing vanadium titanomagnetite pellets(CVTP)with Cr2O3 addition were studied,and the reduction swelling index(RSI)and compressive strength(CS)of the reduced CVTP with simulated coke oven gas(COG)injection were investigated.The results showed that the CS of the CVTP decreases and the porosity of the CVTP increases with increasing amount of Cr2O3 added.The Cr2O3 mainly exists in the form of(Cr,Fe)2O3 solid solution in the CVTP and as Fe-Cr in the reduced CVTP.The CS of the reduced CVTP increases and the RSI of the reduced CVTP decreases with increasing amount of Cr2O3 added.The limited aggregation and diffusion of metallic iron contribute to the formation of dense lamellar crystals,which leads to the slight decrease for reduction swelling behavior of reduced CVTP.This work provides a theoretical and technical basis for the utilization of CVTP and other Cr-bearing ores such as chromite with COG recycling technology.

Porous solid inspired hyper-crosslinked polymer liquids with highly efficient regeneration for gas purification

Separation media that combine the desired material properties within a single material for a given process remain an ongoing challenge for the gas separations in industry.Process integration of porous solid adsorbents is difficult due to their limited volumetric capacity,whereas issues of volatility and high regeneration temperatures exist for liquid amines and physical solvents.Herein,we report a family of polymer liquids inspired by hyper-crosslinked polymers(HCPs),a class of highly swellable network polymers.Compared with a chemically similar porous solid,the HCP-liquids demonstrate good volumetric capacity and improved selectivity of carbon dioxide over methane.Uptake appears to be enhanced by intramolecular swelling of the HCP-liquids at elevated pressures,while guests are strongly rejected from the HCP-liquids at slightly elevated temperatures,leading to highly efficient regeneration.Heat of adsorption and specific heat capacity of the HCP-liquids are also low,further suggesting favourable process thermodynamics.Additionally being easily prepared at scale,the presented HCP-liquids represent a promising step towards a material with the requisite properties to replace conventional scrubbing solvents to drastically reduce the footprint and energy needs of gas separations.