Effects of repeated water exchange and the molecular-weight distribution of PVA cast gels on the elution of polymers

The elution behaviors of polymers from hydrogels are studied using repeated water exchange on poly(vinyl alcohol) (PVA) gels. Physically cross-linked PVA gel was prepared using a cast-drying method from several powders with a high degree of hydrolysis (98.5 mol%) and varying degrees of polymerization (500, 1000, 1700, and 2400). The gels were immersed in water, which was then repeatedly exchanged with and without an immediate drying process. The elution of polymers from a PVA cast gel was estimated by quantitatively measuring the total carbon in the solvent water using a total organic carbon analyzer; a measurement was taken each time the solvent water was exchanged, and the amount of polymers eluted approached zero after sufficient water exchange. The total amount of polymers eluted is dependent on the degree of polymerization of the PVA powders. Additionally, the molecular-weight distributions of the PVA powders used for gelation and the polymers eluted in the solvent water were evaluated using a high performance liquid chromatography. The average molecular-weight of the eluted polymers was less than that of the PVA powders. The elution behaviors during repeated water exchange are discussed on the basis of the amount eluted and the molecular-weight distribution of the eluted polymers; these factors are dependent on the nature of the PVA powders.     

Synthesis,Characterisation, and Evaluation of a Cross-Linked Disulphide Amide-Anhydride-Containing Polymer Based on Cysteine for Colonic Drug Delivery

The use of disulphide polymers, a low redox potential responsive delivery, is one strategy for targeting drugs to the colon so that they are specifically released there. The objective of this study was to synthesise a new cross-linked disulphide-containing polymer based on the amino acid cysteine as a colon drug delivery system and to evaluate the efficiency of the polymers for colon targeted drug delivery under the condition of a low redox potential. The disulphide cross-linked polymers were synthesised via air oxidation of 1,2-ethanedithiol and 3-mercapto-N-2-(3-mercaptopropionamide)-3-mercapto propionic anhydride (trithiol monomers) using different ratio combinations. Four types of polymers were synthesised: P10, P11, P151, and P15. All compounds synthesised were characterised by NMR, IR, LC-MS, CHNS analysis, Raman spectrometry, SEM-EDX, and elemental mapping. The synthesised polymers were evaluated in chemical reduction studies that were performed in zinc/acetic acid solution. The suitability of each polymer for use in colon-targeted drug delivery was investigated in vitro using simulated conditions. Chemical reduction studies showed that all polymers were reduced after 0.5–1.0 h, but different polymers had different thiol concentrations. The bacterial degradation studies showed that the polymers were biodegraded in the anaerobic colonic bacterial medium. Degradation was most pronounced for polymer P15. This result complements the general consensus that biodegradability depends on the swellability of polymers in an aqueous environment. Overall, these results suggest that the cross-linked disulphide-containing polymers described herein could be used as coatings for drugs delivered to the colon.     

Investigation of liquid crystalline and photocrosslinkable poly[4‐x‐phenyl‐4′‐(m‐methacryloyloxyalkyloxy)cinnamate]s

Three series of liquid‐crystalline‐cum‐photocrosslinkable polymers were synthesized from 4‐x‐phenyl‐4′‐(m‐methacryloyloxyalkyloxy)cinnamates (x = ? H, ? OCH₃ and ? CN; m = 6, 8 and 10) by free radical solution polymerization using azobisisobutyronitrile as an initiator in tetrahydrofuran at 60 °C. All the monomers and polymers were characterized using intrinsic viscosity, and FTIR, ¹H NMR and ¹³C NMR spectroscopy. The liquid crystalline behavior of these polymers was examined using a hot stage optical polarizing microscope. All the polymers exhibited liquid crystalline behavior. The hexamethylene spacer‐containing polymers exhibited grainy textures; in contrast, the octamethylene and decamethylene spacer‐containing polymers showed nematic textures. Differential scanning calorimetry data confirmed the liquid crystalline property of the polymers. Thermogravimetric analysis revealed that all the polymers were stable between 236 and 344 °C in nitrogen atmosphere and underwent degradation thereafter. As the methylene chain length increases in the polymer side‐chain, the thermal stability and char yield of the polymers decrease. The photocrosslinking property of the polymers was investigated using the technique of exposing the polymer solution to UV light and using UV spectroscopy. The crosslinking reaction proceeds via 2π–2π cycloaddition reactions of the ? CH?CH? of the pendant cinnamate ester. The polymers containing electron‐releasing substituents (? OCH₃) showed faster crosslinking than the unsubstituted polymers and those containing electron‐withdrawing substituents (? CN). Copyright © 2007 Society of Chemical Industry     

Thermal and viscoelastic structure–property relationships of model comb-like poly(n-butyl methacrylate)

A range of comb polymers of poly(n-butyl methacrylate), where the degree of polymerization (DP) of both the backbone and branches was controlled using RAFT-mediated free-radical polymerization, was synthesized using the method of Vosloo et al. [Macromolecules 2004;37: 2371]. Individual architectural parameters (branch length, branch number and DP of the comb backbone) of these relatively monodisperse samples were systematically varied in order to study the impact of each structural parameter on the thermal and rheological properties of the resulting comb polymers. Differential scanning calorimetry showed lower glass transition temperatures for the comb polymers compared to the original linear backbones. There were negligible differences in glass transition temperatures between comb polymers containing branches of different lengths, and between comb polymers containing backbones of narrow and of broad molecular weight distributions. These observations suggest that because the comb polymers are very tightly spaced, the branches act in the same way as long chain polyBMA. Viscoelastic properties of the comb polymers were investigated using dynamic mechanical analysis, using time–temperature superposition to extend the rheological data over a wide frequency range. Major differences in the viscoelastic responses of the original linear backbones and the comb polymers were observed, which were explained in terms of arm retraction/relaxation leading to tube dilation. All comb polymers showed viscoelastic responses that are characteristic of combs, but differences in responses due to changes in branch length and branch number were difficult to detect. This was mainly due to the relatively high number of branches, whose retractions occurred over a broad frequency range, and thus dominated the observed changes in moduli, thereby possibly masking subtle differences in responses.     

Novel concept of polymers preparation with high photoluminescent quantum yield

A series carbazolyl-containing polymers were synthesized by anionic polymerization of various oxiranes and methyl methacrylate. The polymerization was carried out using as initiator carbazylpotassium activated 18-crown-6 in THF. The polymers were prepared and found using size exclusion chromatography to have a degree of polymerization (DP_n) about 20 relatively and low dispersity in the range of 1.07–1.66. Their optical properties were investigated by means of UV–vis and photoluminescence spectroscopies. The obtained polymers emitted light with maximum emission about 370 nm and high quantum yield ranging up to 79 %. Thus, it was confirmed that the utilization of fluorophore initiator for polymerization of non photoresponsive monomers is quite efficient for the preparation of photoluminescent polymers.     

Novel biocidal polymers based on branched and linear poly(hydroxystyrene)

New biocidal polymers based on branched as well as linear poly(p-hydroxystyrene) were synthesized. Biocidal polymers were synthesized in two steps by creation of active centers via chloroacetylation of linear and branched poly(p-hydroxystyrene) using chloroacetyl chloride. The second step involves the immobilization of onium salts onto the chloroacetylated polymers. All the prepared polymers were characterized using elemental microanalysis, FT-IR, ¹H NMR spectra, and TGA. Antimicrobial activity of the prepared polymers was tested against various pathogenic microorganisms. The antimicrobial activity was found to be affected by the active group and the tested microorganism. The phosphonium salts showed higher activity than ammonium salts.     

Tailoring of energetic groups in acroyloyl polymers

Acryloyl based novel energetic monomers having nitro acrylates and nitro triazole acrylates were synthesized and further used for polymerization. Due to scavanging properties of nitro groups, syntheses of nitro aromatic polymers are not facile at normal conditions. In this regard, we report a simple protocol to synthesize these energetic group embeded acroloyl polymers. These polymers were characterized by FTIR, and NMR spectroscopic techniques. gel permeation chromatography (GPC) technique was employed in order to understand molecular mass of these polymers along with average molecular weight, number average weight and poly dispersity index. Glass transition temperature (T_g) was determined by using DSC analysis. It was observed that with increase in nitro groups in polymers there is a decrease in glass transition temperature. Two steps degradation were depicted in the TGA thermograph in nitro containing polymers. Heat release during this reaction was found up to 951 J/g. Increase in nitrogen content in polymer unit enhanced the heat release of polymers.     

Organoiron Polyelectrolytes: Synthesis and Characterization of Cationic Cyclopentadienyliron Complexes of Polyarylether-Imines

The synthesis of an aromatic ether complex of cyclopentadienyliron containing two terminal aldehyde groups was achieved via metal-mediated nucleophilic aromatic substitution reactions. This dialdehyde monomer was subsequently reacted with a variety of aliphatic and aromatic diamines to produce the corresponding soluble cationic organoiron polyether-imines. These cationic organometallic polymers were characterized using IR, ¹H, and ¹³C NMR, viscosity and thermogravimetric analysis. Viscosity measurements showed that these polymers exhibited polyelectrolyte effects in DMSO solutions. Thermogravimetric analysis showed that decoordination of the iron moieties occurred at about 300°C for polymers with aliphatic spacers in their backbones, while the cyclopentadienyliron moieties were cleaved from the polymers with aromatic spacers in their backbones at about 200°C. Photolytic demetallation of the organoiron polymers resulted in the removal of the pendent cyclopentadienyliron moieties and allowed for the isolation of their organic analogs. While the organoiron polymers were soluble in polar organic solvents, the corresponding organic polymers exhibited very limited solubilities or were insoluble. The organic polymers had glass transition temperatures between 101 and 120°C     

Multi-step precipitation separation system using mixture of thermosensitive polymers

Summary Multi-step precipitation separation system was developed by using aqueous mixtures of some thermosensitive polymers. The following three polymers were used here; poly(N-n-propylacrylamide), poly(N-isopropylacrylamide), and poly(N-isopropylmethacrylamide). A mixture of the three polymers showed three endothermic peaks, and the peak top temperatures were almost consistent with that of the each polymer solution. The polymers were purified by thermal precipitation to obtain fractions which can respond in narrow temperature ranges prior to use. In the case of the precipitation separation of two polymers mixtures, purities of the obtained precipitate and supernatant fractions became high comparing with the case in which the unpurified polymers were used. Parts of the polymers which were not the precipitation targets were also precipitated by the separation procedures. This was caused not only by insolubilization of the non-targeted polymers due to their phase transitions but also by their non-specific entanglement with the targeted polymers. The purities of the fractions also improved when the difference of the phase transition temperature between two polymers was large enough to avoid the coprecipitation. In the case of the precipitation separation of mixtures of the three polymers, purities of each fraction also improved when the purified polymers were used.     

Structural Basis for Intumescence—Part II: Synthesis and Characterization of Intumescent Polymers Containing Spirophosphorus Moiety in the Backbone

Taking the spirophosphorus compound 3,9-dichloro-2,4,8,10-tetraoxo-3,9-diphosphaspiro-[5,5]-undecane-3,9-dioxide as one of the reactive monomers, a family of aromatic spirophosphates was synthesized using dihydric phenols, viz., resorcinol, hydroquinone, 4,4′–dihydroxydiphenyl, bisphenol-A and fluorene dicarbinol as the other monomers. The polymers were synthesized employing melt condensation technique under vacuum and characterized using FT-IR, ¹H-, ¹³C- and ³¹P-NMR spectroscopic methods. The number average molecular weight of the polymers was determined using vapour phase osmometry. Thermal properties of the polymers were studied using differential scanning calorimetry and thermogravimetry techniques. These studies indicated that the polymers containing spirophosphato moiety undergo eruptive degradations in the temperature region 310°–380°C leading to the formation of dense carbonaceous foam. The present study confirmed the spirophosphate structure as an essential requirement to show intumescence.     

A method for preparing water soluble cyclic polymers

A novel ring-closure method was developed to specifically focus on the preparation of water soluble cyclic polymers. The well-defined linear polymers were synthesized by a standard RAFT polymerization using a functional RAFT agent 1. The cyclic polymers were then obtained by virtue of an efficient bromomaleimide-thiol substitution reaction to ring-close the linear precursors. This technique is unique in that it not only produces various well-defined water soluble cyclic polymers with high efficiency and topology purity, but also employs the environmentally benign solvent, water, as the ring-closure reaction media.     

Synthesis and Properties of Polyarylene ether Nitrile Copolymers

Polyether nitrile and its copolymers were synthesized by nucleophilic substitution reaction of 2,6-dichlorobenzonitrile with resorcinol and with varying mole proportions of resorcinol and hydroquinone. The polymers were characterized by different physico-chemical techniques. Thermogravimetric studies showed that all the polymers were stable up to 400°C with a char yield of above 48% at 900°C in N₂ atmosphere. The glass transition temperature was found to increase with increase in concentration of hydroquinone units in the polymer; however no trend was observed in their crystalline melt temperatures. Copolymer composition was determined using FT-IR technique. Crystallinity of the polymers was also studied using wide angle X-ray diffraction.     

Antimicrobial and biodegradable materials based on ε-caprolactone derivatives

Appropriate wound care is pivotal in preventing wound and postsurgery infections, which remain a serious clinical problem. In this study, we report the successful fabrication of antimicrobial and biodegradable materials for possible use in the medical field. Amino functionalized polycaprolactone (PCL [Poly(CL-co-ACL)]) was synthesized via ring opening polymerization. This polymer was then functionalized via the pendant amine to induce antimicrobial efficacy. This was done through the grafting of poly(lysine) onto the amine as well as the quaternization of the amine using alkyl halides. The chemical structures of the synthesized monomers and polymers were confirmed using nuclear magnetic resonance (¹H NMR and ¹³C NMR) spectroscopy and attenuated total reflection-Fourier transform infrared spectroscopy. The molecular weights of the polymers were determined using gel permeation chromatography. Nanofibre scaffolds were produced from the polymers using the electrospinning technique and these were characterized though scanning electron microscopy. The antimicrobial efficacy of the fabricated materials was tested against the Gram-positive (Staphylococcus aureus ATCC 25923) and Gram-negative (Pseudomonas aeruginosa ATCC 27853) bacteria using the disc diffusion and shake flask methods. The polymers demonstrated excellent antimicrobial efficacy. The fibers were exceptionally biodegradable which opens a lot of applications in the biomedical space.     

Activated polymers. II: Synthesis and exchange reactions of biologically active poly(8-acryloxyquinoline)

The monomer 8-acryloxyquinoline (8-AQ) was prepared through the reaction of 8-hydroxyquinoline with either acryloyl chloride or acrylic acid in the presence of triethylamine or N,N-dicyclohexylcarbodiimide, respectively . The resulting monomer was polymerized by free radical polymerization using dimethylformamide (DMF) as a solvent and 2,2^'-azobisisobutyronitrile (AIBN) as an initiator. The reactions of the resulting polymers with hydroxyl and amino compounds have been studied. The polymers were characterized by IR and ¹HNMR spectroscopy. Some of the synthesized polymers were tested for their antimicrobial activity against bacteria and fungi. Generally, all the polymers were effective against the tested microorganisms, but their growth-inhibition effects varied.     

A new approach to 3-miktoarm star polymers using a combination of reversible addition-fragmentation chain transfer (RAFT) and ring opening polymerization (ROP) via “Click” chemistry

The synthesis of AB₂-type miktoarm star polymers using a combination of reversible addition-fragmentation chain transfer (RAFT), ring opening polymerization (ROP) and “Click” chemistry was demonstrated in this work. An azide functional RAFT agent was used to polymerize butyl acrylate, polyethylene glycol acrylate and N-isopropylacrylamide monomers. Propargylamine was reacted with glycerine carbonate to obtain a dihydroxy functional alkyne compound which was used for the ring opening polymerization of ?-caprolactone (?-CL) and lactide. The resulting alkyne functional polycaprolactone (PCL) and polylactide (PLA) polymers were reacted with azide functional polymers in the presence of copper bromide (CuBr) catalyst to obtain miktoarm star polymers. The polymers were characterized by gel permeation chromatography (GPC), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance (NMR) spectroscopy. The star polymers had low polydispersity (∼1.3) with well-defined structures. These polymers have a number of potential applications including crosslinking agents for polyurethane (PU) coatings for biodegradable and fouling release applications.     

Surface modification of UHSPE fibers through allylamine plasma deposition. I. Infrared and ESCA study of allylamine plasma formed polymers

Allylamine (CH₂?CH? CH₂? NH₂) was polymerized through rf generated plasma at varying powers and times. Chemical groups and elemental compositions in the polymers were studied using ESCA and infrared spectroscopy. It was observed that plasma derived polymers contained a significant number of primary amines, along with some secondary and tertiary amines, imines, and nitrile groups. Plasma derived polymers had a complex structure and contained unsaturated groups. A considerable amount of oxygen, primarily from residual air in the plasma reaction chamber, and possibly from atmosphere when plasma polymers were exposed to air, was responsible for carbonyl, amide, ether, and hydroxyl groups found in the polymer structure. Some silicon was also detected in the plasma deposited films.     

Synthesis and characterization of some polyazomethine conducting polymers and oligomers

Polyazomethine polymers were prepared from the polycondensation of terephthaldehyde with different diamines, namely, benzidine, 2,3-diaminopyridine, 1,4-diaminoanthraquinone and 3,5-diamino-1,2,4-triazole. The electrical conductivities of the polymers were studied with doping with H₂SO₄ and 5% I₂ together with the undoped polymers. The crystallinity and morphology of the polymers were studied using XRD and scanning electron microscopy. A comparative study of the electrical conductivities of oligomers of polyazomethines and those of their corresponding polymers was performed. Received: 8 January 1997/Accepted: 10 May 1997     

Synthesis,Characterization, Antimicrobial Activity,and Adhesive Property of Amino Benzyl Group Substituted Acrylic/Methacrylic Polymers and Their Copolymers

The monomers 2-aminobenzylacrylate (2-ABA) and 2-aminobenzyl methacrylate (2-ABMA) were synthesized. The homopolymers and various compositions of copolymers with ethoxylated bisphenol-A-dimethacrylate (EBPADMA) were synthesized using free radical polymerization. The polymers were characterized by FT-IR, ¹H NMR, and ¹³C NMR spectral techniques. The thermal property of the polymers was determined by thermogravimetric analysis and differential scanning calorimeter. The prepared adhesives were tested on leather and metal surfaces using single-lap-joint shear test method. The antimicrobial activity of polymers and copolymers has been studied using Mueller Hinton Broth method.     

Synthesis of new amphiphilic water‐stable hyperbranched polycarbosilane polymers

New amphiphilic hyperbranched polymers possessing hydrophobic skeletons and hydrophilic terminal groups have been prepared and characterized. The synthetic strategy involved the formation of a new stable matrix with aromatic units within a carbosilane backbone, as well as the use of a classical polycarbosilane matrix. Both of them with allyl groups on the surface have narrow polydispersity values. Molecular weight and polydispersity of the hyperbranched polymers were obtained using gel permeation chromatography with multi‐angle light scattering, and determination of the average number of functional groups present on the surface was achieved using ¹H NMR spectroscopy. The introduction of ionic groups was carried out via thiol–ene reactions with various thiol derivatives. The thermal properties of the polymers were also analysed using differential scanning calorimetry and zeta potential measurements. © 2013 Society of Chemical Industry