Asymmetrically Substituted Poly(diitaconates) Obtained by Reversible Addition‐Fragmentation Chain Transfer (RAFT) Polymerization: Synthesis,Copolymerization Parameters,and Antimicrobial Activity

Asymmetrically substituted poly(diitaconate) copolymers are synthesized from 1‐((N‐tert‐butoxycarbonyl)‐2‐aminoethyl)‐4‐propyl diitaconate (PrIA) and different comonomers (N,N‐dimethyl‐acrylamide, DMAA; acrylic acid; or ((N‐tert‐butoxycarbonyl)‐2‐aminoethyl)methacrylate) by reversible addition–fragmentation chain transfer polymerization (RAFT). The RAFT copolymerization parameters of PrIA and DMAA are r_DMAA = 0.49 and r_PrIA = 0.17, compared to r_DMAA = 0.52 and r_PrIA = 0.54 obtained by free radical copolymerization (FRP). Thus, the RAFT process has a stronger trend to alternating polymerization than the FRP process. The polydispersity index of the RAFT copolymers is around 1.2–1.8, compared to 2.8–2.9 for the corresponding FRP copolymers. After removal of the tert‐butoxycarbonyl protective groups, antimicrobially active synthetic mimics of antimicrobial peptides are obtained. The thus activated poly(PrIA‐co‐DMAA) copolymers (repeat unit ratio 1:1) have an increasing activity against Escherichia coli and Staphylococcus aureus with increasing molar mass. The RAFT copolymers are slightly more active and less toxic than comparable FRP polymers, leading to a higher selectivity for bacteria over mammalian cells. Higher molar fractions of PrIA in poly(PrIA‐co‐DMAA) copolymers (up to 80 mol%) do not increase their antimicrobial activity; reduction of the BuIA content in poly(BuIA‐DMAA) (down to 10 mol%) leads to a loss of activity against both E. coli and S. aureus.     

Synthesis and Characterization of Solution Processable Poly(pyrazolines)

Solution‐processable poly(dibenzalacetone) and poly(dibenzalcyclohexanone) are prepared by the condensation of 1,4‐dialkoxy‐bisbenzaldehyde and acetone/cyclohexanone using classic Claisen–Schmidt condensation. The prepared polymers are readily soluble in common organic solvents due to the presence of alkoxy chains present on the aromatic ring. The availability of α,β‐unsaturated ketone on the backbone is readily functionalized with hydrazine hydrate to obtain poly(pyrazoline acetate), a nonconjugated polymer on the backbone, which shows enhanced emission characteristics on comparison with the pristine polymer and small molecule analogues. The highest occupied molecular orbital–lowest unoccupied molecular orbital (HOMO–LUMO) of levels of poly(pyrazolines) has a band gap of 1.54 eV as calculated from cyclic voltammetry and UV–vis studies. Uniform thin film is obtained by spin casting as 1% solution on chlorobenzene and annealing under vacuum. Atomic force microscopy analysis shows fine morphology of the thin film. I–V characterization of the film shows low turn‐on voltage of 5.3 V. HOMO–LUMO is calculated by density functional theory and the result suggests that these molecules have great potential toward polymer organic light‐emitting diode applications.     

Conducting Poly(anilineboronic acid) Nanostructures: Controlled Synthesis and Characterization

Self‐doped poly(anilineboronic acid) (PABA) nanostructures have been prepared by chemical polymerization in an aqueous acid solution and aliphatic alcohols. In aliphatic alcohols, PABA is soluble under the polymerization conditions. According to ¹¹B NMR studies, the formation of anionic tetrahedral boronate ester in aliphatic alcohols in the presence of fluoride forms the basis of self‐doped, soluble PABA. Transmission electron microscope images show the formation of nanostructures with different shapes and forms in different solvents after precipitation of the polymer as a result of ion exchange in the presence of 0.5 M HCl. The spectroscopic and cyclic voltammetric results confirm the formation of conducting PABA nanostructures in high yield. The conductivity of PABA thin films made from the nanostructures prepared in aqueous acid, methanol, ethanol and 1‐propanol is approximately 15 and 3.0, 2.1 and 1.9 S · cm^?1, respectively. The conducting PABA nanostructures are processable since they are easily re‐dispersed in the various solvents up to approximately 5 mg · mL^?1. UV‐vis kinetic measurements, XPS and ¹¹B NMR results suggest that the formation of various nanostructures is influenced by the polymerization rate, the degree of self‐doping versus external doping, and the polarity of the solvents used. The PABA nanostructured films produced from these structures exhibit enhanced redox stability in a wider potential window in non‐aqueous media compared to polyaniline due to formation of six‐member heterocyclic complexes containing a boron‐imine dative bond resulting in a self‐doped self‐cross‐linked polymer. The degree of crosslinking depends on the nature of nanostructures. In non‐aqueous media, the self‐doped, self‐cross‐linked PABA nanostructured films are much less susceptible to cathodic and anodic degradation at extreme potentials, overcoming a major limitation of more common conducting polymers.

     

New Cationic Biodegradable Poly(Urethane-co-Ester): Synthesis,Structural Characterization,Modification and Gene Delivery

To improve the transfection efficiency of poly(urethane-co-ester) and the cytotoxicity of PEI25k with DNA, we synthesized a new poly(urethane-co-ester), PUE, bearing ester linkages and amino groups in the backbone and urethane linkages in the side-chain, and then prepared a binary mixture, PUE-PEI25k, using a physical blending method. The structure of PUE was confirmed by FT-IR and NMR spectra. Both poly(urethane-co-ester), PUE, and binary mixture PUE-PEI25k, readily self-assembled with plasmid DNA (pCMV-βgal) in a HEPES buffer, were characterized by dynamic light scattering. The results revealed that PUE and PUE-PEI25k were able to self-assemble plasmid DNA into PUE/DNA and PUE-PEI25k/DNA nano-complexes small enough to enter a cell through endocytosis. Titration studies were performed to determine the buffering capacities of PUE and PUE-PEI25k. The COS-7 cell viability in the presence of PEI25k, PUE and PUE-PEI25k was studied. At low mass ratio of PUE/PEI25k (150:1), it was found that the PUE-PEI25k/DNA complexes were able to transfect COS-7 cells in vitro with a high efficiency comparable to a well-known gene carrier, PEI25k/DNA. The results indicate that the binary mixture PUE-PEI25k is an attractive cationic carrier for gene delivery and an interesting candidate for further study.     

Thermo-Sensitive Hydrogels Based on Interpenetrating Polymer Networks Made of Poly(N-isopropylacrylamide) and Polyurethane

A series of interpenetrating polymer networks (IPNs) of vinyl-terminated polyurethane (VTPU) and poly(N-isopropylacrylamide) (PNIPAAm) was prepared by free radical polymerization. The effects of IPN composition and cross-linking density on the thermo-responsive and mechanical properties have been studied in terms of particle size, dynamic mechanical thermal properties, transmittance, swelling and de-swelling behavior and water transport mechanism. Results showed that the swelling ability of hydrogels increased over four orders of magnitude in terms of diffusivity, and phase transition became faster with increasing N-isopropylacrylamide (NIPAAm) content. Regarding the mechanical reinforcement of swollen gel, a significant increase in compression properties has been obtained by forming IPNs with polyurethane, which was tailor-made depending on the IPN composition and structure of polyurethane. Furthermore, a cross-linking density increase in the NIPAAm domain augmented rubbery modulus, decreased water swelling and increased water deswelling of the IPNs.     

Poly(acrylic acid)-grafted Poly(N-isopropyl acrylamide) Networks: Preparation,Characterization and Hydrogel Behavior

Poly(acrylic acid)-grafted poly(N-isopropylacrylamide) co-polymer networks (PNIPAAm-g-PAA) were prepared via the reversible addition-fragmentation transfer (RAFT) polymerization of N-isopropyl- acrylamide (NIPAAm) with trithiocarbonate-terminated PAA as a macromolecular chain-transfer agent in the presence of N,N-methylenebisacrylamide. The PNIPAAm-g-PAA co-polymer networks were characterized by means of Fourier transform infrared spectroscopy, differential scanning calorimetry and small-angle X-ray scattering. It is found that the PNIPAAm-g-PAA co-polymer networks were microphase-separated, in which the microdomains of PNIPAAm-PAA interpolymer complexes were dispersed into the PNIPAAm matrix. The PNIPAAm-g-PAA hydrogels displayed a dual response to temperature and pH values. The thermoresponsive properties of PNIPAAm-g-PAA networks were investigated. Below the volume phase transition temperatures, the PNIPAAm-g-PAA hydrogels possessed much higher swelling ratios than control PNIPAAm hydrogel. In terms of swelling, deswelling and reswelling tests, it is judged that the PNIPAAm-g-PAA hydrogels displayed faster response to the external temperature changes than control PNIPAAm hydrogel. The improved thermoresponsive properties of hydrogels are ascribed to the formation of PAA-grafted PNIPAAm networks, in which the water-soluble PAA chains behave as the hydrophiphilic tunnels and allow water molecules to go through and, thus, to accelerate the diffusion of water molecules.     

Blue‐Green Light Emitting Poly(phenylenevinylene) Derivatives as Candidates for Polymer LEDs: Synthesis and Characterization

Summary: Alkoxy substituted derivatives of poly‐ and oligo[(m‐phenylenevinylene)‐alt‐(p‐phenylenevinylene)] were synthesized via the Wittig ( P1 , OPV1 , OPV2 ) and the Wittig‐Horner ( P2 , OPV3 , OPV4 ) condensation routes. The polymers were characterized by ¹³C NMR, ¹H NMR, FT‐IR spectroscopy and GPC. ¹H NMR was a convenient tool to distinguish between the cis and trans double bonds in the compounds. Poly[(4‐decyloxy‐1,3‐phenylenevinylene)‐alt‐(1,4‐phenylenevinylene)] ( P1 ) contained cis and trans double bonds in significant amounts, the vinylene configuration of poly[(4‐decyloxy‐1,3‐phenylenevinylene)‐alt‐(2,5‐dipentyloxy‐1,4‐phenylenevinylene)] ( P2 ) was nearly exclusively trans. Model compounds ( OPV1–4 ) were also synthesized to support the structural and optical characterization. UV‐vis absorption, photoluminescence (PL) and cyclic voltammetry measurements have been performed to investigate the influence of the positions and the number of substituents on electronic levels. The polymers exhibited an intensive solid‐state emission in the blue‐green ( P1 ) and the green ( P2 ) region of the spectrum. Light emitting diodes have been fabricated consisting of ITO, PEDOT:PSS, P2 and Ca/Al. They exhibited high luminance of 100 cd · m^?2 at 5.9 V and low onset voltages (4.3 V) for the electroluminescence (EL).

Schematic representation of a light emitting diode fabricated by use of an alkoxy substituted derivative of poly[(m‐phenylenevinylene)‐alt‐(p‐phenylenevinylene)] ( P2 ).     

Synthesis,Characterization and Properties of a Physically and Chemically Gelling Polymer System Using Poly(NIPAAm-co-HEMA-acrylate) and Poly(NIPAAm-co-cysteamine)

The aim of this work was to develop a simultaneous physically and chemically gelling system using NIPAAm co-polymers. The in situ polymer gel was obtained by synthesizing poly(NIPAAm-co-HEMAacrylate) and poly(NIPAAm-co-cysteamine) through free radical polymerization and further nucleophilic substitution. The purpose of the dual gelation is that physical gelation would take place at higher temperatures as the NIPAAm chains associate, while chemical gelation would occur through a Michael-type addition reaction, resulting in a cross-link forming through a nucleophilic attack of the thiolate on the acrylate. The structure of each co-polymer was then verified using ¹H-NMR and FT-IR spectroscopy. The corresponding lower critical solution temperature and phase transition behavior of each co-polymer was analyzed through cloud point and DSC, while mechanical properties were investigated through rheology. Swelling behavior was also monitored at different temperatures. The resulting polymer system demonstrated properties compatible with physiological conditions, forming a gel at pH 7.4 and at temperatures near body temperature. The hydrogel also showed reduced viscoelastic flow at low frequency stress, and increased strength than purely physical or chemical gels. Swelling behavior was determined to be temperature-dependent; however, no difference was observed in swelling percent beyond 48 h. Having the ability to alter these co-polymers through various synthesis parameters and techniques, this hydrogel can potentially be used as an injectable, waterborne gelling material for biomedical applications such as endovascular embolization.     

Synthesis and Characterization of Poly(arylene ether oxadiazole) Telechelics

Poly(arylene ether oxadiazole) telechelics with fluorine and hydroxyl end groups were synthesized by nucleophilic substitution polymerizations of 2,5‐bis(4‐fluorophenyl)‐1,3,4‐oxadiazole monomer with bishydroxy compounds containing ? C(CH₃)₂, ? C(CF₃)₂ and ? SO₂? groups. Fluorotelechelics were obtained with about 3 repeating units (molecular weight about 2 000 g · mol^?1) using a rather excess (100 mol‐%) of bis(fluorophenyl) oxadiazole compound. On the other hand, hydroxytelechelics were synthesized with about 9 repeating units (molecular weight about 5 000 g · mol^?1) using a small excess of bishydroxy compound (monomer molar ratio of 0.93). Sulfonated poly(arylene ether oxadiazole) hydroxytelechelics were also synthesized using sulfonated and unsulfonated bishydroxy compounds. All sulfonated hydroxytelechelics were partially water soluble, even when only 40 mol‐% of sulfonated monomers was used. The number of repeating units of hydroxytelechelics increased up to 12 (molecular weight about 9 000 g · mol^?1) using sulfonated monomers, probably because of the higher reactivity of sulfonated phenoxide. The molecular weights estimated by ¹H NMR were in agreement to the results obtained by SEC. The telechelics can be used as precursor for the synthesis of block copolymer.

Structure of the hydroxytelechelics.     

Poly(N,N‐dimethylacrylamide)‐block‐Poly(L‐lysine) Hybrid Block Copolymers: Synthesis and Aqueous Solution Characterization

Four poly(N,N‐dimethylacrylamide)‐block‐poly(L ‐lysine) (PDMAM‐block‐PLL) hybrid diblock copolymers and two PLL homo‐polypeptides are prepared via ROP of ε‐trifluoroacetyl‐L ‐lysine N‐carboxyanhydride initiated by primary amino‐terminated PDMAM and n‐hexylamine respectively. The PLL blocks render the copolymers a multi‐responsive behavior in aqueous solution due to their conformational transitions from random coil to α‐helix with increasing pH, and from α‐helix to β‐sheet upon heating. The random coil‐to‐α‐helix transition is found to depend on the PLL length: the longer the peptide segment, the more readily the transition occurred. The same trend was observed for the α‐helix‐to‐β‐sheet transition, which was found to be inhibited for short polypeptides unless conjugated with the PDMAM block.

     

Iridium(III) Complexes with PEO and PS Polymer Macroligands and Light‐Emitting Properties: Synthesis and Characterization

Summary: On the basis of terpyridine functionalized poly(ethylene oxide) (PEO) and poly(styrene) (PS), a series of light‐emitting iridium(III) compounds was effectively synthesized. The respective iridium(III) target compounds were prepared by grafting chloro‐bridged precursor complexes [Ir(ppy)₂‐μ‐Cl]₂ (ppy = phenylpyridine) and [Ir(ppy‐CHO)₂‐μ‐Cl]₂ (ppy‐CHO = 4‐(2‐pyridyl)benzaldehyde) onto terpyridine functionalized PEO and PS tails. 1D and 2D NMR characterization was performed revealing the expected resonances. Gel permeation chromatography (GPC) proved the stability and purity of the targeted materials. Preliminary investigations of the light‐emitting properties were carried out by standard methods such as UV‐vis and steady‐state luminescence spectroscopy. The morphology and the quality of films of these iridium(III) compounds were furthermore investigated using AFM. Improved stability on the electrode surface was illustrated using cyclic voltammetry. One of the polymer materials was compared to the neat complex, which showed quick degradation.

Green and orange light‐emitting iridium(III) complexes with two cyclometalating ligands and one terpyridine ligand with PS tails.     

聚乳酸－乙醇酸共聚物合成与降解

本文对聚乳酸-乙醇酸(PLGA)的合成制备的多种方法进行了阐述,对聚乳酸-乙醇酸(PLGA)的降解性能和降解机理进行了概述.     

Soluble Telechelic Polycondensation Poly(ether ketones): Synthesis and Characterization

The present article reports the synthesis of soluble, propyl‐substituted aromatic ring telechelic polycondensation blocks having molecular weights ranging from 1800 to 6500 g mol^?1 and polymolecularities of 1.3 to 1.7. Chain‐growth polycondensation is performed, and the initiator is selected through reactivity studies, using ¹⁹F nuclear magnetic resonance (NMR) measurements. Gel permeation chromatography, NMR spectroscopy, and matrix‐assisted laser desorption/ionization time of flight mass spectrometry show that blocks are terminated by a methoxy group at one end and a fluorine atom at the other. Polymers are crystalline as synthesized, as shown by X‐ray diffraction and differential scanning calorimetry, do not recrystallize once melted, and undergo solvent‐induced crystallization. Crystalline peak positions and relative intensities are different from those observed for other poly(ether ketones). The difference in crystal form is proposed to stem from packing disruption related to the presence of propyl substituents. Thermogravimetry shows a good thermal resistance up to 450 °C.     

Synthesis of Di‐block Copolymers Containing Regioregular Poly(3‐hexylthiophene) and Poly(tetrahydrofuran) by a Combination of Grignard Metathesis and Cationic Polymerizations

Poly(3‐hexylthiophene)‐block‐poly(tetrahydrofuran) was synthesized by cationic ring‐opening polymerization of tetrahydrofuran (THF) using a poly(3‐hexylthiophene) macroinitiator. Poly(3‐hexylthiophene) macroinitiator used for the ring‐opening polymerization of THF was synthesized by reacting the hydroxypropyl end‐group with trifluoromethanesulfonic anhydride in the presence of 2,6‐di‐tert‐butylpyridine. ¹H NMR spectroscopy and SEC data confirmed the formation of the di‐block copolymers. Field‐effect mobility of poly(3‐hexylthiophene)‐block‐poly(tetrahydrofuran) was measured in a thin‐film transistor configuration and was found to be 0.009 cm² · V^?1 · s^?1.

     

Synthesis,Characterization and Properties of Poly(butylene succinate) Reinforced by Trimellitic Imide Units

Summary: A series of high molecular weight poly(butylene succinate) copolyester containing rigid imide units were synthesized in this paper. The chemical structure and composition of the copolyesters were determined by ¹H NMR spectroscopy and Fourier transform infrared spectroscopy (FT‐IR). Gel permeation chromatography (GPC) was employed to determine the molecular weight and molecular weight distribution. The differential scanning calorimetry (DSC) technique showed that the melting temperature (T_m) of the copolyester decreased slightly with the increment in trimellitic imide unit content. When the imide unit content was increased to 6.3 mol‐%, it had an elongation at break of 510% (83% higher than that of PBS) and a tensile strength of 37 MPa (7% higher than that of PBS). The changes in mechanical properties of the copolyester might be owed to the compositive effects of spherulitic morphology and imide units.

FT‐IR spectra of PBS and PBST.     

Thermoresponsive UCST‐Type Behavior of Interpolymer Complexes of Poly(ethylene glycol) and Poly(poly(ethylene glycol) methacrylate) Brushes with Poly(acrylic acid) in Isopropanol

Upper critical solution temperature (UCST)‐type thermoresponsive behavior of poly(ethylene glycol)–poly(acrylic acid) (PEG–PAA) and poly(poly(ethylene glycol) methacrylate)–poly(acrylic acid) (PPEGMA–PAA) interpolymer complexes has been observed in isopropanol. For these investigations, PPEGMA and PAA with various average molecular weights have been synthesized by atom transfer radical polymerization. It has been found that both the PEG and PPEGMA have lower cloud point temperatures (T _cp) than its mixed polymer solutions with PAA, whereas PAA does not show such behavior in the investigated temperature range. These findings indicate the reversible formation of interpolymer complexes with variable structure and composition in the solutions of the polymer mixtures in isopropanol. Increasing the ethylene glycol/acrylic acid molar ratio or the molecular weight of either the PAA or the H‐acceptor PEG component of the interpolymer complexes increases the UCST‐type cloud point temperatures of these interpolymer systems. The polymer–polymer interactions by hydrogen bonds between PAA and PEG or PPEGMA and the correlations between T _cp and structural parameters of the components revealed in the course of these investigations may be utilized for exploring well‐defined UCST‐type material systems for various applications.

     

Synthesis of a heparinized poly(organophosphazene)

The synthesis of a new potential anti-thrombogenic polymer is described. Limited halogenation of an aryloxysubstituted polyphosphazene, followed by quaternization with triethylamine yielded a polymer capable of forming polyelectrolyte complexes with sodium heparin. The results of preliminary clotting tests with bovine blood are presented.     

Synthesis of Cyclic Poly(methyl methacrylate) Directly from Dihalogenated Linear Precursors

Cyclic poly(methyl methacrylate) (PMMA) is prepared by intramolecular radical trap‐assisted atom transfer radical coupling (RTA‐ATRC) of dihalogenated PMMA precursors. The inclusion of the radical trap nitrosobenzene (NBz) in the coupling sequence affords high yields of cyclic polymers, as observed by gel permeation chromatography and confirmed by ¹H NMR and electrospray ionization mass spectra, which show the presence of the aromatic group from the NBz incorporated into the cycle. Analogous coupling reactions in the absence of the radical trap do not lead to appreciable cyclization or even intermolecular elongation, consistent with chain‐end sterics preventing radical–radical coupling as the predominant termination pathway. Thermolysis of the cyclic PMMA, possible because of the labile C? O bond in the alkoxyamine linkage contained in the macrocycle, causes a reversion back to the linear form and is consistent with the role of the radical trap in the coupling sequence. Differential scanning calorimetry is also used to compare cyclic PMMA with its linear analog, with a marked increase in glass transition temperatures found after cyclization.

     

Surface modification of poly(ether ether ketone) with methacryloyl-functionalized phospholipid polymers via self-initiation graft polymerization

To improve blood compatibility of poly(ether ether ketone) (PEEK), surface modification with methacryloyl-functionalized phospholipid polymers was performed through self-initiation graft polymerization. The copolymers (PMA) of 2-methacryloyloxyethyl phosphorylcholine (MPC) and 2-aminoethyl methacrylate hydrochloride were synthesized by conventional free radical polymerization. The PMA was then immobilized with pentafluorophenyl methacrylate to obtain methacryloyl-functionalized MPC polymers (PMAMA). The degree of substitution of the methacryloyl group into the copolymer was nearly completed. The PMAMA was dissolved in 1-butanol and the solution was dropped on PEEK. UV light (350?±?50?nm) was subsequently irradiated on PEEK for various periods. Elemental analysis of the PEEK surface was performed by X-ray photoelectron spectroscopy and phosphorus and nitrogen signals due to the MPC units on PEEK were observed. The surface wettability of PEEK was also improved by immobilization of PMAMA. Plasma protein adsorption was effectively reduced on the PMAMA-immobilized surface regardless of the type of protein. Furthermore, PMAMA immobilization was also useful in reducing platelet adhesion on PEEK. In conclusion, methacryloyl-functionalized MPC polymers could be immobilized on PEEK by simple photo-irradiation, resulting in significant improvement in blood compatibility.     

Rapid Synthesis and MALDI‐ToF Characterization of Poly(ethylene oxide) Multiarm Star Polymers

Multiarm PEO star polymers with a purely aliphatic polyether structure have been synthesized using hyperbranched polyglycerol (PG) with different molecular weights as a multifunctional initiator. Different degrees of deprotonation of the initiator were studied with respect to molecular weight control. The results show that the degree of deprotonation is a crucial parameter for the synthesis of well‐defined polymers with controlled molecular weights. Partial deprotonation of the PG hydroxyl groups (5–8%) was proven to represent an optimum for the synthesis of star polymers with molecular masses close to the theoretical values. Molecular weights of the stars ranged between 9 000 and 30 000 g · mol^?1. MALDI‐ToF spectra confirmed that the PEO arms in the star polymers possess homogeneous lengths.