Polyacrylamide Blocks Research Articles

Characterization of polyacrylamide diblock copolymers by mass spectrometry combined with Mass-remainder analysis (MARA)

Polyacrylamide block copolymers has been extensively used in many fields of science and technology due to their water solubility, biocompatibility and smart and tunable properties. In this study, we used the Mass-remainder analysis (MARA) and the Multi-step Mass-remainder analysis (M-MARA) for the processing of complex MALDI-TOF mass spectra of a series of poly(N-acryloylmorpholine)-block-poly(N-isopropylacrylamide) diblock copolymers. It was found that selection of the MARA base mass unit affects the shape of the Mass remainder versus m/z plots enabling to draw conclusions about the length and diversity of the blocks. Even better and more informative visualization can be achieved by creating 2-step M-MARA plots. The comprehensive characterization of the poly(N-acryloylmorpholine)-block-poly(N-isopropylacrylamide) copolymers with various block length were performed, and the results were confirmed by nuclear magnetic resonance (NMR) spectroscopy.

One‐For‐All Polyolefin Functionalization: Active Ester as Gateway to Combine Insertion Polymerization with ROP, NMP, and RAFT

AbstractThis work develops the Polyolefin Active‐Ester Exchange (PACE) process to afford well‐defined polyolefin–polyvinyl block copolymers. α‐Diimine PdII‐catalyzed olefin polymerizations were investigated through in‐depth kinetic studies in comparison to an analog to establish the critical design that facilitates catalyst activation. Simple transformations lead to a diversity of functional groups forming polyolefin macroinitiators or macro‐mediators for various subsequent controlled polymerization techniques. Preparation of block copolymers with different architectures, molecular weights, and compositions was demonstrated with ring‐opening polymerization (ROP), nitroxide‐mediated polymerization (NMP), and photoiniferter reversible addition–fragmentation chain transfer (PI‐RAFT). The significant difference in the properties of polyolefin–polyacrylamide block copolymers was harnessed to carry out polymerization‐induced self‐assembly (PISA) and study the nanostructure behaviors.

One-For-All Polyolefin Functionalization: Active Ester as Gateway to Combine Insertion Polymerization with ROP, NMP, and RAFT.

This work develops the Polyolefin Active-Ester Exchange (PACE) process to afford well-defined polyolefin-polyvinyl block copolymers. α-Diimine PdII -catalyzed olefin polymerizations were investigated through in-depth kinetic studies in comparison to an analog to establish the critical design that facilitates catalyst activation. Simple transformations lead to a diversity of functional groups forming polyolefin macroinitiators or macro-mediators for various subsequent controlled polymerization techniques. Preparation of block copolymers with different architectures, molecular weights, and compositions was demonstrated with ring-opening polymerization (ROP), nitroxide-mediated polymerization (NMP), and photoiniferter reversible addition-fragmentation chain transfer (PI-RAFT). The significant difference in the properties of polyolefin-polyacrylamide block copolymers was harnessed to carry out polymerization-induced self-assembly (PISA) and study the nanostructure behaviors.

Dual control of external surface and internal pore structure of small ordered mesoporous silica particles directed by mixed polyion complex micelles

A versatile approach has been developed to prepare small mesoporous silica particles with simultaneous control of the internal ordered pore structure and the external particle surface. Mixed polyion complex (PIC) micelles are used as silica structure-directing agents: they result from the complexation of a polybase with two polyacid double-hydrophilic block copolymers (DHBC) having either a poly(ethylene oxide) (PEO) based-block or a polyacrylamide (PAM) block. The ionizable block in both DHBC is poly(acrylic acid), which complexes oligochitosan to form the core of the electrostatic complex. By varying the architecture of the PEO-based block (linear or comb-shaped) and the synthesis parameters, it is possible to modulate the pore structure from 3D cage-like to 2D-hexagonal and lamellar mesostructures. Replacing a fraction of the PEO-based polymers with DHBC having a polyacrylamide block that has no affinity for silica is shown to affect silica-micelle interactions and material growth. While the PEO chains interact with silica to form the hybrid interface, the PAM chains act as capping agents and control the external surface of the particles. Increasing the relative amount of PAM-based DHBC leads to the formation of small discrete mesoporous silica particles that are reduced in size to 200 nm. The particle size reduction and particle surface stabilization by PAM chains can be explained by considering not only the existence of a mixed corona of PAM and PEO in PIC micelles but also the differentiated solubility of these two neutral blocks induced by silica condensation. Thus, the present strategy allows independent decrease of the particle size and tuning of its pore structure.

Polymer electrolyte membranes based on PEO-containing block copolymers

Triblock copolymers comprising chemically complementary poly(ethylene oxide)/polyacrylamide (TBC) and their partially hydrolyzed derivative (TBChydr) were investigated as possible ion-conducting membranes for Li-ion batteries (LBs), dye-sensitized solar cells (DSSCs) and fuel cells (PEFCs). Two TBC samples consisting PEO blocks of variable block length (MnPEO = 6·104 and 3.5·104 kDa) were synthesized and used for these purpose. It was noticed that ionic conductivity of TBC membranes increases with PEO block lengthening from 6.2·10−11 to 3.2·10−9 S⋅cm−1. The introduction of additional ionic groups -COOH in polyacrylamide block of TBC has a positive effect on the conductive characteristics of copolymer membranes. The ionic conductivity of TBC membranes filled with LiPF6 increases with increasing of salt content.

Synthesis of IONP's decorated graft copolymers and study of their magnetic force–induced wastewater treatment

Our work is focused on facile synthesis and modification of amylopectin‐grafted block copolymers by using reversible addition−fragmentation chain transfer (RAFT) polymerization technique. This technique yields polymers with controlled molecular weight and low polydispersity indexes and is feasible with a wide range of monomers. Five different grades of amylopectin‐grafted polymethacrylic acid and polyacrylamide block copolymers have been synthesized via RAFT, by varying the amount of acrylamide employing amylopectin‐based macro chain transfer agent. Graft copolymers have been upgraded as smart responsive graft copolymers, through the incorporation of iron oxide nanoparticles (IONPs) via condensation reaction. The polymeric materials have been extensively characterized by energy‐dispersive X‐ray analysis, Fourier transform infrared spectroscopy, proton magnetic resonance spectroscopy, scanning electron microscopy, ultraviolet‐visible spectroscopy, gel permeation chromatography, transmission electron microscopy, thermogravimetric analysis, and X‐ray diffraction analysis. Normal and responsive graft copolymers have been studied for removal of model contaminant (kaolin), and responsive graft copolymers have been used to remove methylene blue dye (without using any adsorbent) from water by applying external magnetic field. The upgraded block copolymers have shown best performance in wastewater treatment.

Synthesis of Fluorine-containing Polyacrylamide Block Copolymer and Their Application for Rapidly Formation of Sub-10 nm Microdomains

Synthesis of Fluorine-containing Polyacrylamide Block Copolymer and Their Application for Rapidly Formation of Sub-10 nm Microdomains

CO2-responsive polyacrylamide copolymer vesicles with acid-sensitive morpholine moieties and large hydrophobic RAFT end-group

Sequential Reversible Addition Fragmentation Chain Transfer (RAFT) polymerizations using 2,2′-azobis[2-(2-imidazolin-2-yl)propane]dihydrochloride (VA-044) and 2-(dodecylthiocarbonothioylthio)-2-methylpropionic acid (DDMAT) were used to give amphiphilic polyacrylamide block copolymers containing N-(2-morpholin-4-ylethyl)acrylamide (MEA), where the morpholine moieties are CO2-responsive. The order in which monomers were polymerized determined the placement of the large hydrophobic RAFT end group with more complex ABA′ type self-assembly (e.g. patterned and large worm-like vesicles, large compound micelles) obtained when the dodecyl trithiocarbonate end-group was attached to the hydrophilic poly(MEA) block. Cleaving the hydrophobic end group reverts self-assembly to simpler spherical vesicles observed in the triblock of the same chemical composition, but with the RAFT end group attached to the hydrophobic poly(tert-butyl acrylamide) block. Ionization of the hydrophilic poly(MEA) block through flushing with CO2 irreversibly shifts self-assembly towards lower order morphologies with spherical micelles being more favoured than vesicles.

Block copolymers containing polyacrylamide and polyacrylic acid: Bulk structure and hydrogen bonds system

ABSTRACTAsymmetric block copolymers PAAc-b-PAAm (DBCs) and PAAm-b-PAAc-b-PAAm (TBCs) comprised poly(acrylic acid) blocks of constant chain length and polyacrylamide blocks of variable chain length were synthesized using RAFT/MADIX technique. Their properties in a bulk state were studied by differential scanning calorimetry and the hydrogen bond system was investigated by Fourier transform infrared spectroscopy. It was found that DBCs and TBCs possess a homogeneous amorphous structure, whose temperatures of glass transition and destruction beginning increased with growth of PAAm block length. The H-bond system between PAAc and PAAm blocks was most developed in TBC sample and formed manly by the mixed cyclic dimmers of carboxyl and amide groups.

Block Copolymer Brushes for Completely Decoupled Control of Determinants of Cell–Surface Interactions

AbstractThe known determinants for cell–surface interactions, comprising biochemical cues, patterns, passivating functionality, and control of tether mechanical properties, are fully decoupled in tailored block copolymer brushes synthesized by surface‐initiated atom transfer radical polymerization. Exploiting sequential polymerization of a passivating underlying polyacrylamide (PAAm) block with defined cross‐linking followed by a second poly(acrylic acid) block, which can be conjugated with a selective adhesion peptide, hierarchically structured brushes that can be micro‐patterned by soft lithography were obtained. The interaction of NIH 3T3 fibroblasts and PaTu 8988t pancreatic tumor cells with brushes that differed only in the stiffness of the hidden PAAm block or only in the peptide ligand, while keeping all other parameters constant, revealing profound differences in cell adhesion and morphology. In particular, cells could only attach well to stiff RGD presenting brushes.

Block Copolymer Brushes for Completely Decoupled Control of Determinants of Cell-Surface Interactions.

The known determinants for cell-surface interactions, comprising biochemical cues, patterns, passivating functionality, and control of tether mechanical properties, are fully decoupled in tailored block copolymer brushes synthesized by surface-initiated atom transfer radical polymerization. Exploiting sequential polymerization of a passivating underlying polyacrylamide (PAAm) block with defined cross-linking followed by a second poly(acrylic acid) block, which can be conjugated with a selective adhesion peptide, hierarchically structured brushes that can be micro-patterned by soft lithography were obtained. The interaction of NIH 3T3 fibroblasts and PaTu 8988t pancreatic tumor cells with brushes that differed only in the stiffness of the hidden PAAm block or only in the peptide ligand, while keeping all other parameters constant, revealing profound differences in cell adhesion and morphology. In particular, cells could only attach well to stiff RGD presenting brushes.

Synthesis of styrene–acrylamide copolymer by surfactant‐free sonicated dynamic interfacial polymerization

This paper summarizes a study on emulsifier‐free ultrasonically assisted in situ dynamic interfacial emulsion copolymerization process of acrylamide and styrene. The resulting emulsions are stable and uniform for several months. Thermogravimetric analysis (TGA) curves and reaction conversion measurements have provided an important knowledge regarding the emulsifier‐free polymerization method. Solvent extractions (water, methanol, and xylene) have shown that the polymerization product is essentially a styrene–acrylamide copolymer. The copolymer produced is a block copolymer, PS‐b‐PAM, where each block contains small amounts of the other comonomer. The produced emulsions are film forming at room temperature in spite of the very high block Tgs, owing to a unique water plasticization effect of the polyacrylamide blocks. Some films prepared from the PS‐b‐PAM have resulted in clear and transparent films. The presented interfacial dynamic polymerization process is fast, reaching 81% conversion within 2 hr of sonication at 4°C (low temperature owing to molecular weight and kinetic considerations), and produces very stable PS‐b‐PAM emulsions. TGA was extensively used as an analytical tool for determination of the reaction parameters and composition of the acrylamide–styrene copolymers. Copyright © 2011 John Wiley & Sons, Ltd.

Hydrophobically modified polyacrylamide block copolymers for fast, high‐resolution DNA sequencing in microfluidic chips

By using a microfluidic electrophoresis platform to perform DNA sequencing, genomic information can be obtained more quickly and affordably than the currently employed capillary array electrophoresis instruments. Previous research in our group has shown that physically cross-linked, hydrophobically modified polyacrylamide matrices separate dsDNA more effectively than linear polyacrylamide (LPA) solutions. Expanding upon this work, we have synthesized a series of LPA-co-dihexylacrylamide block copolymers specifically designed to electrophoretically sequence ssDNA quickly and efficiently on a microfluidic device. By incorporating very small amounts of N,N-dihexylacrylamide, a hydrophobic monomer, these copolymer solutions achieved up to approximately 10% increases in average DNA sequencing read length over LPA homopolymer solutions of matched molar mass. Additionally, the inclusion of the small amount of hydrophobe does not significantly increase the polymer solution viscosities, relative to LPA solutions, so that channel loading times between the copolymers and the homopolymers are similar. The resulting polymer solutions are capable of providing enhanced sequencing separations in a short period of time without compromising the ability to rapidly load and unload the matrix from a microfluidic device.

EVALUATION OF FOCUSED AND UNFOCUSED SHOCK WAVE PROPAGATION IN POLYACRYLAMIDE GEL AND PORCINE TISSUE.

Background Extracorporeal shock wave therapy (ESWT) has been shown to increase perfusion in ischemic cardiac tissue and increase autograft healing in both animal models and clinical studies. To help clarify the mechanisms by which ESWT induces tissue healing, we studied the propagation of focused and unfocused shock wave sources in animal tissue by comparing the cavitation pattern in polyacrylamide gel and porcine tissue. Study Design and Method Fifteen percent polyacrylamide blocks, marble-embedded polyacrylamide, and porcine thigh were treated with a focused shock wave source with an OssatronTM machine and unfocused shock wave source with a StorzTM device. Cavitation patterns were visualized using a MicroMaxxTM ultrasound machine immediately after a treatment. Results Focused shock wave treatment of polyacrylamide gel with the OssatronTM produced a focal ellipsoidal cavitation field with a 2 cm depth. An increase in treatment energy or intensity resulted in a more intense cavitation field with a larger diameter. Focused treatment of the marble-embedded gel produced a disturbance of the marble-gel interface with increased cavitation intensity at increased treatment energy. Unfocused shockwave treatment of the polyacrylamide gel produced a focal cavitation field superficially at the site of treatment. However, the cavitation field displayed a radiating pattern with deeper propagation into the gel. Increasing the treatment intensity led to a corresponding increase in the intensity of the cavitation field. Unfocused shock wave treatment of marble-embedded gel showed no observable change in the marble-gel interface. Treatment of porcine thigh with both focused and unfocused shock wave at low and high energy and intensity did not produce any observable changes. Conclusion The result of ESWT in polyacrylamide gel indicates that deep tissue stimulation with an unfocused shock wave source may not yield any benefits because high tissue impedance may reduce shock wave propagation. However, focused shock wave may be more favorable for deep tissue stimulation.

Whole cell immobilization of Ralstonia pickettii for lipase production

Different matrices viz. agar, alginate and polyacrylamide were examined for the immobilization of whole cells of Ralstonia pickettii. The enzyme activity of whole cells immobilized in agar beads was very low. Alginate beads had the inherent disadvantage of dissolving in phosphate based media and even glutaraldehyde treatment did not have any significant effect. A Tris–HCl system was found to be the best for alginate based immobilization of whole cells from R. pickettii and 4% alginate beads gave an optimal lipase activity of 14 U/ml per min. When different concentrations of polyacrylamide were tried for immobilization of R. pickettii whole cells, 15% polyacrylamide blocks showed a retention activity of 66% (25 U/ml per min) when compared to that of the free cells (40 U/ml per min). Bis-acrylamide concentration of 0.15 g/10 ml of buffer was ideal and the optimum whole cell concentration for polyacrylamide immobilization was 2.0 g/l of saline. Optimal immobilized whole cell concentration (polyacrylamide blocks) for lipase production was 20% and polyacrylamide blocks were reused three times effectively for lipase production. Of the three matrices examined for the immobilization of whole cells from R. pickettii, polyacrylamide gave the best performance.

Characteristic of Poly(vinyl alcohol)-polyacrylamide Block Copolymers with Pendent Styrylpyridinium. (1). Dynamic Viscoelasticity.

Characteristic of Poly(vinyl alcohol)-polyacrylamide Block Copolymers with Pendent Styrylpyridinium. (1). Dynamic Viscoelasticity.