Transport properties of polyphosphates related to natural teichoic acids

The paper deals with transport functions of natural polyphosphates, i.e. wall-and lipoteichoic acids (WTA, LTA) appearing in Gram-positive bacteria. The results concerning the separation of magnesium and calcium ions in a membrane system, simulating bacteria cell wall, are presented. The system was composed of a solid polymer membrane and a liquid membrane, containing poly(trimethylene phosphate) and α-hydroxy-ω-(2-ethylhexyl)-poly(trimethylene phosphate) applied as synthetic analogues of WTA and LTA, respectively. Up-hill transport with reference towards magnesium ions was observed.     

Organic–Inorganic Interactions in Poly(trimethylene carbonate)–Titania Hybrids

Polycarbonate–titania hybrids have been synthesized by a sol–gel reaction, starting from poly(trimethylene carbonate) (PTMC) and titanium isoproproxide in different ratios. PTMC with a given chain length was obtained by ring opening polymerization. FT‐IR spectra reveal the presence of Ti O C covalent bonds between organic and inorganic phases, and their number increases with increasing inorganic phase content. Solvent extractions show that hybrid soluble fraction contains low PTMC chains with isopropoxide ends, which suggests that Ti O C bond formation is mainly promoted by transesterification reactions of isopropyl alcohol onto the polymer chain, catalyzed by Ti compounds. Hybrid thermal properties reflect the combined effect of the decrease of PTMC molecular weight and of bond formation between PTMC and the inorganic network. The nanometric dimension of the TiO₂ domains, confirmed by atomic force microscopy, provides optically transparent hybrids.

     

Synthesis,Characterization and In Vitro Cytotoxicity of Poly[(5‐benzyloxy‐trimethylene carbonate)‐co‐(trimethylene carbonate)]

The ring‐opening copolymerization of 5‐benzyloxy‐trimethylene carbonate (BTMC) with trimethylene carbonate (TMC) was described. The polymerization was carried out in bulk at 150°C using stannous octanoate as initiator. The influence of reaction conditions such as polymerization time and initiator concentration on the yield and molecular weight of the copolymers were investigated. The poly(BTMC‐co‐TMC)s obtained were characterized by FT‐IR, ¹H NMR, ¹³C NMR, GPC and DSC. NMR results of copolymer showed no evidence for decarboxylation occurring during the propagation. The relationship between the copolymer glass transition temperature and composition was in agreement with the Fox equation. The in vitro cytotoxicity studies of the poly(BTMC‐co‐TMC) (50 : 50) using 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide (MTT) assay demonstrated that the copolymer has low cytotoxicity compared to poly[(lactic acid)‐co‐(glycolic acid)] (75 : 25).     

Synthesis and polymerization of 2-(p-methacryloyloxybenzoyl)ethyl 2′-(phthalimido)ethyl hydrogen phosphate

Benzyl 2-(p-methacryloyloxybenzoyl)ethyl 2′-(phthalimido)ethyl phosphate ( 3 ) and 2-(p-methacryloyloxybenzoyl)ethyl 2′-(phthalimido)ethyl hydrogen phosphate ( 6 ) were prepared, characterized, and polymerized with 2,2′-azoisobutyronitrile (AIBN). The properties of the resultant polymers are described.     

Magnesium and calcium ions transport by synthetic analogues of teichoic acids with 1,2- and 1,3-linked phosphodiester units

2-Ethylhexylpoly(trimethylene 1,3-phosphate) ( 3 ), poly(1,2-glycerol phosphate) ( 1 ) and poly-(1-acetoxy-2,3-glycerol phosphate) ( 2 ) were synthesized and used as synthetic analogues of teichoic acids. Their properties as a carrier of magnesium and calcium ions were examined in the competitive exchange diffusion process with the countertransport of hydrogen or sodium ions. It turned out that polymers with 1,2-glycerol phosphate units ( 1,2 ) exhibit lower ability to transport preferentially magnesium ions than poly(1,3-alkylene phosphate)s ( 3 ). In all cases the efficiency of polyphosphates in preferential transport of magnesium ions is higher when transport is coupled with proton counterflow.     

Synthesis and Characterization of Poly(trimethylene oxide)‐block‐Polystyrene and Poly(trimethylene oxide)‐block‐Polystyrene‐block‐Poly(methyl methacrylate) by Combination of Atom Transfer Radical Polymerization (ATRP) and Cationic Ring‐Opening Polymerization (CROP)

Summary: Diblock copolymers, poly(trimethylene oxide)‐block‐poly(styrene)s abbreviated as poly(TMO)‐block‐poly(St), and triblock copolymers, poly(TMO)‐block‐poly(St)‐block‐poly(MMA)s (MMA = methyl methacrylate), with controlled molecular weight and narrow polydispersity have been successively synthesized by a combination of atom transfer radical polymerization (ATRP) and cationic ring‐opening polymerization using the bifunctional initiator, 2‐hydroxylethyl α‐bromoisobutyrate, without intermediate function transformation. The gel permeation chromatography (GPC) and NMR analyses confirmed the structures of di‐ and triblock copolymers obtained.

GPC curves of (a) poly(St); (b) diblock copolymer, poly(St)‐block‐poly(MMA) before precipitation; (c) poly(St)‐block‐poly(MMA) after precipitation in cyclohexane/ethanol (2:1); (d) triblock copolymer, poly(TMO)‐block‐poly(St)‐block‐poly(MMA).     

Synthesis and drug release behavior of poly (trimethylene carbonate)-poly (ethylene glycol)-poly (trimethylene carbonate) nanoparticles

ABA-type triblock copolymers poly (trimethylene carbonate)-poly (ethylene glycol)-poly (trimethylene carbonate) were synthesized by ring-opening polymerization of trimethylene carbonate initiated by dihydroxyl poly (ethylene glycol). The critical micelle concentration of amphiphilic triblock copolymers in aqueous solution was determined by fluorescence spectroscopy using 9-chloromethyl anthracene as fluorescence probe. Core-shell-type nanoparticles were prepared by the dialysis technique. Transmission electron microscopy images showed that these nanoparticles were regularly spherical in shape. Micelle size determined by dynamic light scattering is 50-160 nm. Anticancer drug methotrexate (MTX) as model drug was loaded in the polymeric nanoparticles. X-ray powder diffraction spectra showed that model drugs were molecularly dispersed in the core. In vitro release behavior of MTX was investigated.     

Synthesis and Non‐Isothermal Crystallization Characteristics of Poly[(ethylene)‐co‐(trimethylene terephthalate)]s

A series of random copolyesters were synthesized by the bulk polycondensation of dimethyl terephthalate with ethylene glycol (EG) and trimethylene glycol (TMG) in various compositions. Their composition, molecular weight, and thermal properties were determined. The copolymers containing 22.2 mol‐% ≤ TMG ≥ 46.0 mol‐% are crystallizable while the other copolymers containing 32.8 mol‐% ≤ TMG ≤ 39.3 mol‐% are amorphous. Non‐isothermal crystallization exotherms were measured over the cooling rate of 2.5–20.0 K/min by calorimetry and analyzed by the Avrami method. For the crystallization at 2.5 K/min, the Avrami exponent n was estimated to be in the range of 2.91–3.81, depending on the composition. The results suggest that the primary crystallization follows a heterogeneous nucleation and spherulitic growth mechanism. However, when the cooling rate increases and the content of the minor component unit (EG or TMG) increases, the crystallization behavior becomes deviated from the prediction of the Avrami analysis, which is due to the involvement of secondary crystallization and the achievement of relatively low crystallinity. The crystallization rate is accelerated by increasing cooling rate but retarded by incorporating the minor component into the polymer backbone. In addition, the activation energy in the crystallization was estimated.     

Solution properties and chain dimensions of poly(trimethylene sulfide)

Poly(trimethylene sulfide) (PTS) synthesized by means of anionic polymerization was studied with regard to its solubility behaviour and unperturbed chain dimensions. The Flory-Huggins interaction parameter was used to determine the solubility parameter of PTS, δ = 10,0 cal^1/2 · cm^?3/2, which agrees with the calculated one. PTS fractions were isolated by means of fractional precipitation from chloroform/hexane at 50°C. Their number-average molecular weight, M?_n, and the intrinsic viscosity, [η], were measured in chloroform at 25°C. From these data the relation [η] = 3,10 · 10^?4 M? was estimated. A value of the characteristic ratio, 〈r²〉₀/(n l²) = 4,0, was determined from the Burchard-Stockmayer-Fixman plot, which shows that this chain molecule has high flexibility.     

Polymers of carbonic acid, 28. SnOct2‐initiated polymerizations of trimethylene carbonate (TMC, 1,3‐dioxanone‐2)

SnOct₂ (Sn(II) 2‐ethylhexanoate) initiated polymerizations of TMC were studied either in conc. chlorobenzene solution at 80°C or in bulk at temperatures ≥ 120°C. Benzyl alcohol added as coinitiator accelerated the polymerization process and allowed a control of the number‐average molecular weight (M_n) via the monomer/coinitiator ratio (M/C). The formation of benzyl carbonate endgroups allowed in turn the determination of (M_n) via ¹H NMR endgroup analyses. Model reactions suggest that at 80°C intermediately formed Sn‐alkoxide groups play the role of the true initiator. At 140, 160 or 180°C neat SnOct₂ polymerized TMC in such a way that polyTMC having octanoate endgroups was formed. Variation of the monomer/initiator (M/I) ratio at 160°C enabled again a proper control of M_n via the M/I‐ratio and high molecular weight polyTMC was obtained. The influence of back‐biting degradation on the molecular weight was also studied at 160°C to find the optimum time‐temperature window.     

Thermodynamics of 2‐Methyltrimethylene Urethane,its Polymerization in Bulk and of Poly(2‐methyl‐trimethylene urethane) Between 0 and 335 K

In an adiabatic vacuum calorimeter the temperature dependence of the heat capacity C ⁰_p of crystalline 2‐methyltrimethylene urethane (MTU; systematic name: 5‐methylperhydro‐1,3‐oxazin‐2‐one) and of amorphous poly(2‐methyltrimethylene urethane) [PMTU; systematic name: poly(5‐methyl‐2‐oxo‐1‐oxa‐3‐azahexamethylene)] was studied between 6 and 335 K with an uncertainty of about 0.2%. In a calorimeter with a static bomb and an isothermal shield the energies of combustion ΔU_comb of the monomer and of the polymer were measured. From the experimental data the thermodynamic functions C ⁰_p (T), H ⁰(T)–H ⁰(0), S ⁰(T), G ⁰(T)–H ⁰(0) were calculated in the range of 0 to 340 K, and enthalpies of combustion ΔH⁰_comb and thermodynamic parameters of formation ΔH ⁰_f, ΔS ⁰_f, ΔG ⁰_f of the substances studied were estimated at T = 298.15 K and standard pressure. The configurational entropy S ⁰_conf of the polymer was estimated. The results were used to calculate the thermodynamic characteristics of MTU polymerization in bulk (ΔH ⁰_pol, ΔS ⁰_pol, ΔG ⁰_pol) with ring‐opening and formation of linear PMTU in the range of 0 to 340 K.     

A novel synthetic route to poly(β-ketone)s via poly(alkoxyethyne)s

Isopropoxyethyne (1a) and tert-butoxyethyne (1b) were polymerized using group 5 and 6 transition metal catalysts to give poly(isopropoxyethyne) (2a) and poly(tert-butoxyethyne) (2b) , respectively. The weight-average molecular weight (M?_w) of the resulting poly(alkoxyethyne)s was up to 1.0 × 10⁴. Among the transition metal catalysts, a tungsten alkoxide or a molybdenum alkoxide having low Lewis acidity were found to effectively promote the polymerization without causing side reactions. Poly(tert-butoxyethyne) was successfully converted to poly(β-ketone) 3 by acid hydrolysis of the tert-butyl vinyl moiety.     

Synthesis and Photovoltaic Properties of a D–A Copolymer Based on the 2,3‐Di(5‐hexylthio­phen‐2‐yl)quinoxaline Acceptor Unit

A new D–A copolymer ( PBDT‐DTQx) based on the 2,3‐di(5‐hexylthiophen‐2‐yl)quinoxaline acceptor unit and a bithienyl‐substituted benzodithiophene (BDT) donor unit is designed and synthesized for application as the donor material in polymer solar cells (PSCs). The polymer film shows a broad absorption band covering the wavelength range from 300 to 720 nm and a low highest occupied molecular orbital (HOMO) energy level at ?5.35 eV. A device based on PBDT‐DTQx :PC₇₀BM ([6,6]‐phenyl‐C71‐butyric acid methyl ester) (1:2.5, w/w) with chloronaphthalene as a solvent additive displays a power conversion efficiency (PCE) of 3.15%. With methanol treatment, the PCE of the PSCs is further improved to 3.90% with a significant increase of the short‐circuit current density, J_sc, from 10.10 mA cm^?2 for the device without the methanol treatment to 11.71 mA cm^?2 for the device with the methanol treatment.

     

Synthesis and properties of star oligo/poly(trimethylene carbonate)s with cholic acid moieties as cores

Star oligo/poly(trimethylene carbonate)s with cholic acid moieties as cores were synthesized by ring-opening polymerization of trimethylene carbonate (TMC) initiated by cholic acid with hydroxyl groups. The molecular weights of the star oligomers/polymers were controlled by adjusting the feed ratio of the initiator cholic acid to the monomer TMC. The star oligo/poly(trimethylene carbonate)s were characterized by Fourier transform infrared spectroscopy (FT-IR), (1)H nuclear magnetic resonance spectroscopy ((1)H-NMR) and combined size-exclusion chromatography and multiangle laser light scattering (SEC-MALLS) analysis. The water contact angles of the star oligo/poly(trimethylene carbonate)s were measured. Using 3-(4,5 dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, the star oligo/poly(trimethylene carbonate) was proved to have a low cytotoxicity. A microsphere drug-delivery system based on a star polymer was fabricated and its in vitro drug release property was studied.     

Synthesis of α,ω‐Isocyanate–Telechelic Poly(methyl methacrylate)

The preparation of α,ω‐isocyanate–telechelic poly(methyl methacrylate) using RAFT polymerization and two postpolymerization modification steps is presented. The synthetic strategy includes the RAFT polymerization of methyl methacrylate, which results in a hetero telechelic polymer. In the first modification step by radical exchange, a carboxylic acid homo telechelic PMMA was successfully prepared. Second, the carboxylic acid end groups are reacted with hexamethylene diisocyanate in excess and magnesium chloride as a catalyst. Under mild reaction conditions (80 °C, 4 h), the isocyanate homo telechelic PMMA is obtained. A conversion of 86% of the carboxylic acid end groups was achieved.