Characterization of poly(butyl acrylate) diols prepared via atom transfer radical polymerization and subsequent modification

We used atom transfer radical polymerization to synthesize poly(butyl acrylate) (PBA) and then substituted the bromo end group with N-ethanol methyl amine to obtain the hydroxyl (OH) end-capped poly(butyl acrylate). A compound of PBA with Mn of about 500 was first synthesized and used as a model compound to investigate the substitution reaction conditions of bromo end group with N-ethanol methyl amine. The OH functionality over 0.8 was obtained when the model compound was reacted with N-ethanol methyl amine under the reaction temperature of 90°C for about 24 h. A poly(butyl acrylate) diol of Mn 2000 with OH functionality of about 1.76 was obtained and characterized by infrared spectrum (IR), hydrogen nuclear magnetic resonance (HNMR) spectra, gel permeation chromatography (GPC) and thermo gravimetric analysis (TGA).     

Modification of poly(octadecene‐alt‐maleic anhydride) films by reaction with functional amines

Thin films of poly(octadecene‐alt‐maleic anhydride) on top of Si wafers and glass plates were modified by reactions with different functional amines to be used in future studies on the relevance of certain molecular surface properties for the covalent immobilization of proteins. For that aim, a strategy was developed and applied to convert the anhydride moieties of the copolymer by functional amines into side chains bearing hydrophilic groups of acidic (carboxylic acid, sulfonic acid), basic (amines), or neutral (poly(ethylene oxide) (PEO), glucose) character. The modification of the copolymer films was achieved through the two‐step formation of a cyclic imide, which was very stable in aqueous solution. Depending on the reactivity of the applied amine, the adjustment of the reaction time was suitable for the preparation of partially converted surfaces of the polymer film. Degrees of modification between 5 and 30% (according to X‐ray photoelectron spectroscopy data) were obtained. Annealing the modified polymer films induced efficient back‐formation of the anhydride groups. By reaction of the layered polyanhydrides with highly crosslinked diamines, amine‐functionalized polymer films were produced that were capable of binding secondary polyanhydride layers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1255–1266, 2003     

Surface modification of PHBV films with different functional groups: Thermal properties and in vitro degradation

Polyacrylamide was photografted on solution‐cast poly(3‐hydroxybutyric acid‐co‐3‐hydroxyvaleric acid) (PHBV) films (amide‐PHBV), on which amide groups were transformed into amine groups through Hofmann degradation reaction (amine‐PHBV), followed by collagen coupling reaction to prepare collagen‐modified PHBV (collagen‐PHBV). Amide‐, amine‐, and collagen‐PHBV had higher water absorption and d‐spacing values than PHBV, and melting temperatures and enthalpies decreased in the order of collagen‐PHBV < amine‐PHBV < amide‐PHBV < PHBV. Thermal decomposition kinetics of PHBV component in the films has been investigated by means of nonisothermal thermogravimetric and derivative thermogravimetric studies. Applying the Avrami‐Erofeev equation with index of 2/5 as the probable kinetic function, the suitable activation energy was calculated by the Friedman method through linear fitting (correlation coefficient > 0.98). The activation energy of PHBV was lower than that of amide‐PHBV but higher than that of amine‐ and collagen‐PHBV. Being incubated in phosphate‐buffered saline at 37°C, the modified PHBV films showed more weight loss than PHBV during 360 days; however, pH of degradation fluids was nearly neutral as the initial pH was recorded at 7.2. The modified PHBV films with different functional groups may provide an improved biodegradation rate for various cytocompatible biomaterials constructs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The chain extension of anionic prepolymers in the preparation of aqueous poly(urethane–urea) dispersions

Anionic polyurethane prepolymers end‐capped with isocyanate groups were dispersed and chain‐extended in aqueous media using three different extension agents: hydrazine, 1,2‐ethylene diamine (EDA) and 1,2‐propylene diamine (PDA). Two types of prepolymer were used. The first was prepared from isophorone diisocyanate (IPDI), α,α‐dimethylol propionic acid (DMPA) and poly(propylene oxide) diol (PPO) and the second from α,α,α′,α′‐tetramethyl‐1,3‐xylylene diisocyanate (m‐TMXDI), poly(caprolactone) diol (PCL) and DMPA. The colloidal particles which formed in the dispersion process and the constituent poly(urethane–urea) chains were characterised by a combination of dynamic and static light scattering, gel permeation chromatography and FTIR spectroscopy. Using EDA as the extender, a study was made of how the degree of extension depended on the molar ratio of amine to isocyanate groups, [NH₂]/[NCO] (= R_{A, I}). It was found that using a stoichiometric balance of isocyanate and amine groups did not lead to high degree of extension, and better chain extension was obtained at lower R_{A, I} values. In a comparative study using stoichiometric balances of isocyanate and amine groups, the degrees of extension obtained using PDA and EDA were approximately the same, while hydrazine was the least effective. Force–extension studies were carried out on samples prepared from films cast from the aqueous poly(urethane–urea) dispersions in order to assess the influence of chain‐extender type and stoichiometry on bulk properties; values of Young's modulus, tensile strength and maximum extension are reported. Copyright © 2003 Society of Chemical Industry     

Peroxide macro‐initiators for improving biodegradability of polymers

Modification of dextrin by tert‐butylperoxy methanol or its acylation with cyclic anhydride containing a peroxide group resulted in macro‐initiators with randomly located peroxide fragments in the polysaccharide. When dextran was oxidized with iodic acid, dialdehydedextran was obtained. Its aldehyde groups reacted with tert‐butyl hydroperoxide to give functional peroxide groups. The content of peroxide fragments depended directly on the ratio of reagents. The resulting macro‐initiators may be used for synthesizing graft copolymers with polystyrene on poly(butyl acrylate) containing polysaccharide. © 2001 Society of Chemical Industry     

Coating of polyelectrolyte multilayer thin films on nanofibrous scaffolds to improve cell adhesion

The adhesion of L929 cells to poly(?‐caprolactone) (PCL) nanofibers was successfully improved via coating with polyelectrolyte multilayer thin films (PEMs), which enhanced the potential of this material as a scaffold in tissue engineering applications. With the electrostatic self‐assembly technique, poly(diallyldimethylammonium chloride) (PDADMAC) and poly(sodium 4‐styrene sulfonate) (PSS) were formed as four‐bilayer PEMs on electrospun PCL nanofiber mats. Because PDADMAC and PSS are strong polyelectrolytes, they provided stable films with good adhesion on the fibers within a wide pH range suitable for the subsequent processes and conditions. PDADMAC and gelatin were also constructed as four‐bilayer PEMs on top of the PDADMAC‐ and PSS‐coated nanofibers with the expectation that the gelatin would improve the cell adhesion. L929 cells from mouse fibroblasts were then seeded on both uncoated and coated scaffolds to study the cytocompatibility and in vitro cell behavior. It was revealed by the 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay that both the uncoated and coated nanofiber mats were nontoxic as the cell viability was comparable to that of those cultured in the serum‐free medium that was used as a control. The MTT assay also demonstrated that cells proliferated more efficiently on the coated nanofibers than those on the uncoated ones during the 48‐h culture period. As observed by scanning electron microscopy, the cells spread well on the coated nanofibers, especially when gelatin was incorporated. The surface modification of PCL nanofiber mats described in this research is therefore an effective technique for improving cell adhesion. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Novel Poly(linolenic acid) Graft Copolymers: Synthesis,Characterization and Electrical Properties

A poly(linolenic acid)‐g‐poly(tert‐butyl acrylate) graft copolymer was synthesized from polymeric linolenic acid peroxide possessing peroxide groups in the main chain by free radical polymerization of tert‐butyl acrylate. Graft copolymers having structures of poly(linolenic acid)‐g‐poly(caprolactone)‐g‐poly(tert‐butyl acrylate) were synthesized from polymeric linolenic acid, possessing peroxide groups on the main chain by the combination of free radical polymerization of tert‐butyl acrylate and ring‐opening polymerization of ε‐caprolactone in one‐pot. The obtained graft copolymers were characterized by proton nuclear magnetic resonance, gel permeation chromatography, thermal gravimetric analysis, differential scanning calorimetry, and scanning electron microscopy techniques. Furthermore, Au/n‐Si diodes were fabricated with and without poly(linolenic acid)‐g‐poly(caprolactone)‐g‐poly(tert‐butyl acrylate)‐4 to form a new interfacial polymeric layer for the purpose of investigating this polymer's conformity in electronic applications. Some main electrical characteristics of these diodes were investigated using experimental current–voltage measurements in the dark and at room temperature.     

Quaternized poly(phenylene oxide) anion exchange membrane for alkaline direct methanol fuel cells in KOH‐free media

A series of anion exchange membrane (AEM) electrolytes with quaternary ammonium moiety are fabricated from poly (phenylene oxide) for its application in alkaline direct methanol fuel cells (ADMFCs). In the first step, poly(phenylene oxide) (PPO) is successfully chloromethylated by substituting chloromethyl groups in the aryl position of polymer. In the second step, the chloromethylated PPO (CPPO) is further homogeneously quaternized and ion‐exchanged to form an AEM. From the second step, series of AEMs are prepared by changing the mole ratio of amine in relation to CPPO. The presence of quaternary ammonium group in the membrane was confirmed by elemental analysis. The fabricated membranes are subjected to cell polarization studies in ADMFCs, wherein quaternized poly(2,6‐dimethyl‐1,4‐phenylene oxide) (CPPO:amine of 1:8) membrane exhibits higher peak power density of 3.5 mW cm^?2 when compared with the other ratios of CPPO:amine in the absence of KOH solution. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43693.     

Micromolding of PDMS scaffolds and microwells for tissue culture and cell patterning: A new method of microfabrication by the self-assembled micropatterns of diblock copolymer micelles

We introduce an innovative fabrication of the polymer scaffolds for tissue culture by utilizing the evaporation induced self-assembled micropatterns of polystyrene-block-poly(acrylic acid) (PS-b-PAA) diblock copolymer micelles. The microstructures were used as templates for micromolding a silicon elastomer, poly(dimethylsiloxane) (PDMS), into tissue scaffolds and microwells for cell patterning purpose. Cultivation of human epithelial cells (Calu-3 cell line) on the PDMS scaffolds demonstrates potential applications in tissue engineering and cell-based biosensors. The reported method is rapid, simple, economical, and versatile comparing with the existing microfabrication techniques.     

Physical properties of water‐borne polyurethane blended with chitosan

Water‐borne polyurethanes based on 4,4‐diphenylmethane diisocyanate, poly(butylene adipate), and chain extender N‐methyldiethanolamine (MDEA) that provided tertiary amine groups were synthesized. The polyurethane–chitosan (PU/CS) blends can be dissolved in the acetic acid and cast into films. The mechanical properties including tensile strength and elongation, as well as the water absorption and thermal properties of the PU/CS films were evaluated. The tensile strength increased with the increased amount of chitosan, but the elongation decreased accordingly. The chitosan in the blends promoted the water absorption. Chitosan was more thermally‐stable than PU, as shown in the thermal gravity analysis. Chitosan also had higher crystallinity, as demonstrated by differential scanning calorimetry. The blends were partial compatible mixtures, based on the data obtained from a dynamic mechanical analysis. Biocompatibility test was conducted utilizing immortalized rat chondrocytes (IRC). After IRC were seeded onto the PU/CS films for 1.5 and 120 h, the number of cells was counted and the morphology of cells was observed by light microscopy and scanning electron microscopy. Blends containing 30% chitosan had more cells attached initially. However, the blends containing more than 70% chitosan appeared to promote the cell proliferation. IRC were round on PU/CS films with more PU, but spread when the chitosan content in blends was higher. Overall, PU/CS films with more chitosan had better mechanical properties as well as biocompatibility. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2683–2689, 2007     

Rapid ambient temperature atom transfer radical polymerization of tert‐butyl acrylate

BACKGROUND: Atom transfer radical polymerization (ATRP) is considered to be one of the better and easier synthetic tools for the preparation of polymers with controlled molecular weights and polydispersities. Ambient temperature ATRP of tert‐butyl acrylate (tBA) was studied in a detailed manner with ethyl 2‐bromoisobutyrate (EBrB) and tert‐butyl 2‐bromoisobutyrate (tBuBrB) as the initiators for three different degrees of polymerization. RESULTS: Details pertaining to the kinetics of polymerization using different initiators are reported. It is observed that dimethylsulfoxide accelerates the polymerization at room temperature. The use of Cu(II) as the deactivator produces very narrow dispersity polymers. A diblock copolymer, poly(tert‐butyl acrylate)‐block‐poly(methyl methacrylate), was synthesized from the poly(tBA) macroinitiator demonstrating the controlled living nature of the polymerizations. CONCLUSIONS: The rate of polymerization is more rapid with a secondary initiator (ethyl 2‐bromopropionate) compared to the tertiary initiators EBrB and tBuBrB. From the detailed kinetic results it is observed that tris(2‐dimethylaminoethyl)amine was a better ligand compared to tris(2‐aminoethyl)amine in terms of achieving controlled polymerization. Copyright © 2007 Society of Chemical Industry     

Graft copolymers from commercial chlorinated polypropylene via Cu(0)‐mediated atom transfer radical polymerization

Commercially available chlorinated polypropylene has been used as a macroinitiator for the Cu(0)‐mediated atom transfer radical polymerization of methyl methacrylate and tert‐butyl acrylate to obtain well‐defined graft copolymers. The relatively narrow molecular weight distribution in the graft copolymers and linear kinetic plots indicated the controlled nature of the copolymerization reactions. Both Fourier transform infrared and ¹H NMR studies confirmed that the graft reactions had taken place successfully. After graft copolymer formation, tert‐butyl groups of poly(tert‐butyl acrylate) side chains were completely converted into poly(acrylic acid) chains to afford corresponding amphiphilic graft copolymers. © 2016 Society of Chemical Industry     

Induction of chirality into a fully sulfonated poly(methoxyaniline) via acid-base interactions with chiral amines

A wide range of chiral amines and amino alcohols associate with poly(2-methoxyaniline-5-sulfonic acid) (PMAS) in aqueous solution, from which optically active PMAS·(amine) films can be cast. The chiral induction is believed to be initiated by acid-base interactions with “free” sulfonic acid groups on the PMAS chains. Chiral amine:PMAS dimer molar ratios as low as 1:4 give PMAS·(amine) films with similar optical activity to those cast from 1:1 molar mixtures, indicating that only one in four of the “free” sulfonate groups on the PMAS chains need to be electrostatically bound by chiral ammonium ions to achieve optimal chiral induction. Circular dichroism studies show that the enantiomeric amines (R)-(+)- and (S)-(−)-1-phenylethylamine induce the opposite helical hands for the supermolecular assemblies of PMAS chains. However, there is no clear correlation between the sign of the CD signals for the PMAS·(amine) films and the configuration of structurally diverse amines.     

Tailored functionalization of low-density polyethylene surfaces

Surface-functionalization chemistries were optimized to tailor the surface chemistry of polyethylene, and this made covalent attachment of bioactive molecules possible. This concept has relevance in biomaterials, biosensors, textiles, and active food-packaging applications. Clean polyethylene films were subjected to chromic acid oxidation to introduce carboxylic acids. A range of functional groups, including amine, aldehyde, thiol, and hydroxyl, were then introduced to the surface of the oxidized films with functionalized crosslinking agents and covalent bioconjugation chemistries. The quantity of functional groups was further increased by subsequent grafting of polyfunctional agents such as polyethylenimine and poly(acrylic acid). The number and type of functional groups were quantified by contact-angle, dye-assay, attenuated total reflectance/Fourier transform infrared, and X-ray photoelectron spectroscopy analyses. We optimized chemistries to introduce a variety of functional groups to the surface of low-density polyethylene in numbers ranging from several picomoles per centimeter squared to tens of nanomoles per centimeter squared. A range of bioactive compounds, including antimicrobials, antibodies, oligonucleotides, cell precursors, drugs, peptides, enzymes, and synthetic biomimetic agents, can be covalently bound to these functional groups in the development of nonmigratory biofunctionalized polymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Dissolving states of cellulose and chitosan in trifluoroacetic acid

Chemical structures of cellulose and chitosan dissolved in trifluoroacetic acid (TFA) and those of cellulose and chitosan films cast from their TFA solutions were studied by ¹³C-NMR and infrared (IR) spectroscopy. Cellulose is trifluoroacetylated selectively at the C6–hydroxyl groups in the TFA solution, and chitosan is dissolved in TFA by forming amine salts with TFA at the C2–amine groups. IR analyses of cellulose films cast from its TFA–acetic acid solutions showed that partly trifluoroacetylated cellulose in the solution state turns to partly acetylated cellulose in the solid state during evaporation of the solvents in air by the ester interchange. Chitosan films cast from its TFA–acetic acid solutions still have the amine salts with TFA. These acetyl groups in cellulose films and TFA in chitosan films are removable by soaking the films in 1N NaOH at room temperature for 1 day.     

Comparison of the effect of six compactin-related compounds on cholesterol synthesis in five human cell types

We have investigated the effect of six compactin-related compounds—mevinolin, compactin, ML-236A, monacolin X, monacolin L and dihydromonacolin L—on cholesterol synthesis in human umbilical vein endothelial cells, human small intestine epithelial cells, human hepatoma cell line HEP G2, normal human skin fibroblasts and in skin fibroblasts from a patient with familial homozygous hypercholesterolemia. The inhibition of cholesterol synthesis was found to depend on both the cell type and the type of compound used. The most effective compounds were mevinolin and compactin. Monacolin X, monacolin L and ML-236A were less effective, and dihydromonacolin L was the least efficacious. Endothelial and epithelial cells were sensitive to very low concentrations of inhibitors (IC₅₀=1.0–30 pg/mL), HEP G2 cells required higher concentrations (IC₅₀=0.01–66 ng/mL) and fibroblasts needed even higher concentrations (IC₅₀=0.1–200 ng/mL). Lactone and acid forms of the inhibitors were equally active. None of the inhibitors had any effect on either protein or fatty acid synthesis in any of the cell types studied. It can be concluded that different compactin-related compounds show a range of potencies as cholesterol synthesis inhibitors and a dose-dependent tissue-selectivity.     

A Synthetic Approach to Star‐Like Polymers of Styrene and Butyl Acrylate by Linking Reactions using Functionalized Methacrylates

Summary: Coupling reactions between terminal functionalized polymer chains were chosen for the synthesis of star‐like polymers consisting of polystyrene and polystyrene‐block‐poly[styrene‐co‐(butyl acrylate)] arms. For the preparation of terminal functionalized polymer chains a side reaction of the 2,2,6,6‐tetramethylpiperidine‐N‐oxyl (TEMPO) mediated free radical polymerization of methacrylates could be used successfully to convert TEMPO terminated polymers into end functionalized polymers. The number of functionalized monomer units attached to the polymer chain is directly related to the TEMPO concentration during this reaction. Different polystyrenes and polystyrene‐block‐poly[styrene‐co‐(butyl acrylate)] block copolymers were functionalized with a variable number of epoxide and alcohol groups at the chain end. For the determination of the optimal reaction parameters for the coupling reactions between these polymer chains, epoxy functionalized polystyrenes were converted with hydroxy functionalized polystyrenes under basic and acidic conditions. By activation with sodium hydride or boron trifluoride star‐like polymers were synthesized under mild conditions. The transfer of the reaction conditions to coupling reactions between end functionalized polystyrene‐block‐poly[styrene‐co‐(butyl acrylate)] copolymers showed that star‐like polymers with more than 12 arms were formed using boron trifluoride as activating agent.

     

Polyurethane/Polylactide-Based Electrospun Nonwovens as Carriers for Human Adipose-Derived Stromal Stem Cells and Chondrogenic Progenitor Cells

Articular cartilage dysfunctions are major cause of pain and disability and lead to serious health complications. Cell-based therapies are proposed as treatment methods for cartilage regeneration. In this study, we proposed polyurethane/poly(L-lactide-co-D, L-lactide)-based electrospun nonwovens as carriers for the delivery of human adipose-derived stromal stem cells. We found that 6:4 and 8:2 polyurethane/poly(L-lactide-co-D, L-lactide) initially enhance proliferative rate of human adipose-derived stromal stem cells, shorten their population doubling time, promote creation of functional chondrogenic nodules during chondrogenic differentiation, improve the collagen-2-to-collagen-1 protein ratio, and upregulate the expression of collagen-2 and aggrecan genes.     

Collagen‐based new biomedicial films: Synthesis,property, and cell adhesion

Grafted‐collagen films with poly(methyl methacrylate), poly(butyl methacrylate), and poly(styrene) were prepared by photoirradiation of the collagen films in the presence of respective monomers. Cell adhesion onto the films was investigated, and the amount of cells adhered onto every grafted films was almost the same as that onto the collagen film crosslinked with glutaraldehyde. Because the swollen grafted films are stronger than the collagen film, they are expected to be good biomedical materials. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2433–2438, 2001     

Novel ionomers based on blends of ethylene-acrylic acid copolymers with poly(vinyl amine)

The polymerization of N-vinyl formamide followed by hydrolysis yields a linear, water-soluble poly(vinyl amine). The high concentration of pendant primary amine groups leads to a polymer with an interesting set of properties. Complexation with water-soluble anionic polyelectrolytes in water solutions leads to a highly water-insoluble material. The study described herein investigated the phase behavior/properties of melt blends of poly(vinyl amine) with ethylene-acrylic acid (EAA) copolymers of less than 10 wt % acrylic acid. The calorimetric and dynamic mechanical analyses of the resultant blends show that the vinyl amine groups are accessible to the acrylic acid groups of the copolymers and the major property changes occur up to the stoichiometric addition of vinyl amine/acrylic acid. At higher levels of vinyl amine (vinyl amine/acrylic acid mol ratio > 4), additional poly(vinyl amine) forms a separate phase. The mechanical, dynamic mechanical, and calorimetric properties of these blends below the stoichiometric ratio show analogous trends as with typical alkali/alkaline metal neutralization. These characteristics relative to the base EAA include improved transparency, lower melting and crystallization temperature, lower level of crystallinity, and increased modulus and strength. The emergence of the β transition in dynamic mechanical testing is pronounced with these blends (as with alkali/alkaline metal neutralization), indicative of microphase separation of the amorphous phase into ionic-rich and ionic-depleted regions. A rubbery modulus plateau for the blends exists above the polyethylene melting point, demonstrating ionic crosslinking. Above 150°C exposure, further modulus increases occur presumably due to amide formation. This study demonstrates that the highly polar poly(vinyl amine) can interact with acrylic acid units in an EAA copolymer comprised predominately of polyethylene (>90 wt %). The thermodynamic driving force favoring ionic association overrides the highly unfavorable difference in composition. © 1996 John Wiley & Sons, Inc.