Step Functionalization Research Articles

High binding capacity surface grafted monolithic columns for cation exchange chromatography of proteins and peptides

Poly(glycidyl methacrylate-co-ethylene methacrylate) monoliths have been prepared in 100 μm i.d. capillaries and their epoxy groups hydrolyzed to obtain poly(2,3-dihydroxypropyl methacrylate-co-ethylene methacrylate) matrix. These polymers were then photografted in a single step with 2-acrylamido-2-methyl-1-propanesulfonic acid and acrylic acid to afford stationary phases for a strong and a weak cation exchange chromatography, respectively. Alternatively, poly(ethylene glycol) methacrylate was used for grafting in the first step in order to enhance hydrophilicity of the support followed by photografting with 2-acrylamido-2-methyl-1-propanesulfonic acid or acrylic acid in the second step. These new columns were used for the separation of proteins and peptides. A mixture of ovalbumin, α-chymotrypsinogen, cytochrome c, ribonuclease A and lysozyme was used to assess the chromatographic performance for large molecules while a cytochrome c digest served as a model mixture of peptides. All tested columns featured excellent mass transfer as demonstrated with very steep breakthrough curves. The highest binding capacities were found for columns prepared using the two step functionalization. Columns with sulfonic acid functionalities adsorbed up to 21.5 mg/mL lysozyme while the capacity of the weak cation exchange column functionalized with acrylic acid was 29.2 mg/mL.

Functionalized polystyrene latex particles as substrates for ATRP: Surface and colloidal characterization

In this work, the process for producing polystyrene particles surface functionalized with a thin shell of ATRP initiator polymerized alone or along with styrene and a crosslinker, is presented. Copolymerization of styrene and acrylic end-capped ATRP initiator to generate a thin shell on the fully polymerized core particles suffered from secondary nucleation owing to their possible incompatibility with the core particles and their own colloidal stability. One step functionalization processes, where the shell forming monomers are added directly to the 70% polymerized core particles, lead to significant changes in the resulting particle morphologies. The shot addition of these monomers led to a very uniform surface morphology without any secondary nucleation owing to quick coalescence of the secondary particles on the soft surface of the seed particles. Addition of crosslinker to the system helped in effectively eliminating the smaller particles generated due to secondary nucleation along with the chemical networking.

Preparation of aminated microfiltration membranes by degradable functionalization using plain PEI membranes with various morphologies

The work describes the functionalization of microporous poly(ether imide) membranes with ultrafiltration separation profile by degradative functionalization using a two-step treatment process, which leads to strongly aminated membranes with microfiltration properties. Membranes with different morphology and ultrafiltration separation profile were prepared. In the first step, the pore system was opened by treatment with diethylenetriamine (DETA) which was followed by a treatment with high molecular poly(ethylene imine) to increase the amount of amine groups. Results verify that macrovoidal structures are more beneficial than sponge-like structures because of their strongly opened pores while only a small reduction in membrane thickness occurred. The separation properties of the virgin membrane have only a marginal influence on the pore opening process because of the leveling off the separation properties after a short treatment time. The number of covalently bound amine functions could be strongly increased by a second step functionalization process using a high-molar volume polyamine as a modifier which indicates the presence of residual imide groups of the basic polymer after the primary DETA treatment. Moreover the prepared membranes are suited for steam sterilization. These characteristics suggest a beneficial application in adsorptive separation processes.

Stable, Hydrophilic Nitrilotriacetic Acid-Capped Gold Monolayer Protected Clusters

ABSTRACTA one step synthesis and functionalization of robust, hydrophilic monolayer protected clusters of gold (Au-MPCs) containing a nitrilotriacetic acid (NTA) is described. The 14 nm Au-MPCs were prepared by the attachment of two bifunctional thioalkylated-poly(ethylene glycol) ligands on the nanoparticles, one containing a nitrilotriacetic acid (NTA) terminal group, while the second hydroxyl (OH) terminated ligand was used as a co-stabilizer to promote the stability of the MPCs. The resulting PEGylated NTA functionalized Au MPCs, which are characterized by TEM, UV-vis and agarose gel electrophoresis are attractive probes for many target species e.g. hexahistidine-tagged proteins. Importantly, the NTA functionality on MPCs ligand shell can be varied.

A novel technique for preparation of aminated polyimide membranes with microfiltration characteristics

In the wet-chemical treatment of polyimide (PI) membranes with aminic modifiers, the modifier molecules will be covalently bound to the membrane polymer. Using modifiers with high aminic nitrogen the amination is combined with a degradation process, which shifts separation properties from ultrafiltration characteristics (untreated membrane) to microfiltration characteristics (treated membrane). Under optimal treatment conditions the steepness of separating curves of the aminated membranes is comparable with the steepness of separating curves of commercial microfilters. Characteristic data of membranes such as water permeability, amine content, SEM morphology, wettability and the dependence of membrane thickness on treatment conditions were presented. Data show that membrane properties are insensitive to modifier concentration in the treatment bath with respect to degradation reaction but sensitive to reaction rate. From the data of amine content per unit surface area of membrane and amine content per unit membrane weight, it was concluded that the functionalization/degradation process is divided in two steps. In the first step functionalization dominates, whereas in the second step functionalization and degradation are simultaneous processes resulting in an equilibrium state. The expected reaction sequence of degradable functionalization is proposed and discussed. Initial membrane morphology seems to be the key parameter for further investigations to optimize membrane preparation processes.

Functionalization of polyolefins by reactive processing: influence of starting reagents on content and type of grafted groups

AbstractPrevious studies carried out in our laboratory on the functionalization of ethylene polymers (homo and copolymers) through free radical processes, using mechanical mixers and/or extruders with diethylmaleate (DEM) and dicumyl peroxide (DCP), have shown that the presence of branched α‐olefin blocks favours degradation versus functionalization and crosslinking whereas these last are more effective with linear ethylene blocks.In this contest the present paper reports about attempts to extend the same processes to propylene polymers by benefitting of the indications of previous results. In particular the one step functionalization of EPM with two or more different groups was carried through the use of different monomers. Moreover the procedure was extended to polypropylene thus obtaining a significant functionalization degree flanked by a remarkable decrease of molecular weight.