Hydroxyl End Research Articles

Block copolymerization of methylmethacrylate via ATRP method using a macroinitiator produced by ring opening polymerization: Characterization, dielectric properties, and a kinetic investigation

ABSTRACTPoly(2-(3-methyl-3-phenylcyclobutyloxirane-co-ϵ-caprolactone) [P(PCBO-co-ϵ-CL)] was synthesized by ring opening polymerization (ROP) of 2-(3-methyl-3-phenylcyclobutyloxirane and ϵ-caprolactone (ϵ-CL) using benzyl alcohol as the initiator and Sn(Oc)2 as the catalyst. To produce a macroinitiator from copolymer with hydroxyl end group was carried out reaction of acylation with choloroacetyl chloride. The molecular structures of copolymers were confirmed by FT-IR, 1H-NMR spectroscopies and gel permeation chromatography (GPC). A kinetic series of methyl methacrylate (MMA) via ATRP method were studied in the presence of this macroinitiator and using CuBr/2,2′-bipyridine (bpy) as catalyst at 110°C. The kinetic study showed that the polymerization proceeded in a controlled way up to high conversions and the number-average molecular weight (Mn) increased depending on time. The thermal properties of copolymers were evaluated by TGA and DSC measurements. The temperature and frequency dependence of dielectric constant (έ) and dielectric loss factor (ϵ″) of P[(PCBO-co-ϵ-CL)-b-PMMA] and that of doped with different concentration of EuCl3 were investigated between the frequency of 100–2000 Hz and temperature range (300–430 K). Also, the ac conductivity has been measured to see the effect of frequency and temperature.

Sequential DMC/FAB-Catalyzed Alkoxylation toward High Primary Hydroxyl, High Molecular Weight Polyether Polyols

A catalytic alkoxylation process to make higher molecular weight poly(propylene oxide) and poly(propylene oxide-co-butylene oxide) polyols containing greater than 65% of primary hydroxyl end groups is described. The one-pot method employs the double metal cyanide catalyst and tris(pentafluorophenyl)borane catalyst (FAB) in a sequential manner and exploits the high primary hydroxyl regioselectivity of FAB over a broad range of temperatures. The process was carried out in two sequential steps: (a) DMC-catalyzed epoxide ring-opening polymerization at a temperature of >130 °C and (b) FAB-catalyzed regioselective capping at a temperature between 60 and 110 °C. The approach thus combines the relative advantages of both the DMC and FAB catalysts: high activity and high primary hydroxyl regioselectivity, respectively. It is also demonstrated that sufficiently low levels of FAB catalyst (e.g., 150 ppm) are sufficient, thus obviating the need for catalyst removal from the final product.

Control of reaction mechanisms in cationically polymerized epoxy resins facilitates the adjustment of morphology and mechanical properties

Structure–property relations of cationically polymerized epoxy thermosets with different morphologies are examined. The morphology adjustment of amorphous epoxy based copolymers and partially crystalline polymer alloys is carried out with star-shaped poly(ε-caprolactone) (SPCL) bearing various numbers of hydroxyl end groups. These hydroxyl groups are known for their reactivity toward epoxides following the activated monomer (AM) mechanism. For this reason, four-armed SPCL was synthesized with four hydroxyl end groups (SPCL-tetraol) and, in addition, with successively esterified ones down to a SPCL with four ester end groups (SPCL-tetraester). SPCL species bearing fewer or no hydroxyl end groups segregate into needle-like nanodomains within the epoxy networks and, if the concentration is high enough, also into crystalline domains. The stronger phase separation of SPCL-tetraester within the epoxy network compared with SPCL-tetraol is due to a reduction of the AM mechanism. The mechanical properties resulting from different morphologies lead to a trade-off between higher storage moduli and Tg values in the case of the more phase separated (and partially crystalline) polymer alloys and higher strain at break in the case of the amorphous copolymers. Nevertheless, in both cases toughness is improved or at least kept on the same level as for the pure epoxy resin. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2188–2199

Chemoenzymatic polymerization of hydrazone functionalized phenol

Hydrazone substituted oligophenol was synthesized via enzymatic oxidative polymerization of (E)-2-((2-phenylhydrazono)methyl)phenol. Enzymatic polymerization catalyzed by Horseradish peroxidase (HRP) enzyme and H2O2 oxidizer yielded oligophenol with hydrazone functionality on the side-chain. Effects of various factors including solvent system, reaction pH and temperature on the polymerization were studied. Optimum polymerization conditions with the highest yield (84%) and molecular weight (M n = 8 × 103, DP ≈ 37, PDI = 1.11) was achieved using MeOH/pH 6.0 buffer (1: 1 vol %) at 25°C in 24 h under air. Synthesized oligomer was characterized by 1H and 13C NMR, FTIR, UV–Vis spectroscopy, GPC, cyclic voltammetry and thermogravimetric analyses. The polymerization involved hydrogen elimination from the monomer, and terminal units of the oligomer structure consisted of phenolic hydroxyl (–OH) end groups. The oligomer backbone possessed phenylene and oxyphenylene repeat units. The resulting oligomer was completely soluble in common organic solvents. The oligomer was thermally robust and exhibited 5% mass loss at 375°C and 50% mass loss at 440°C.

Reactive extrusion of partially crosslinked poly (butylene succinate) via novel vane extruder: thermal, mechanical and rheological properties

In this study, crosslinked poly (butylene succinate) (PBS) was prepared successfully by the reactions of the end hydroxyl groups of PBS with the isocyanate groups of hexamethylene diisocyanate prepolymer (HDIP) using a vane extruder (VE) followed by compression moulding. Torque and gel permeation chromatography showed that the PBS was successfully corsslinked by HDIP. The effects of varied HDIP on properties such as mechanical, thermal properties, and capillary rheological behaviours were also evaluated. The results indicated that HDIP crosslinked PBS with high efficiency. The gel fraction of the crosslinked PBS increased to 57% with the 1.5 wt-% HDIP loading. Differential scanning calorimetry revealed that the cross-link points in the crosslinked samples act as crystal nuclei and the crystallisation temperature increase. Dynamic mechanical analysis revealed that the glass transition temperature (Tg) increased with increase in gel fraction. This may be caused by the reduced molecular chain mobility for corsslinked samples. The capillary rheological properties showed that all samples exhibit non-Newtonian and shear thinning characteristics in the range of applied shear rates, and the apparent viscosity increased with the HDIP content. What's more, the crosslinked PBS also showed improved mechanical properties and thermal stability.

Biotin-targeted Pluronic® P123/F127 mixed micelles delivering niclosamide: A repositioning strategy to treat drug-resistant lung cancer cells

With the aim to develop alternative therapeutic tools for the treatment of resistant cancers, here we propose targeted Pluronic® P123/F127 mixed micelles (PMM) delivering niclosamide (NCL) as a repositioning strategy to treat multidrug resistant non-small lung cancer cell lines. To build multifunctional PMM for targeting and imaging, Pluronic® F127 was conjugated with biotin, while Pluronic® P123 was fluorescently tagged with rhodamine B, in both cases at one of the two hydroxyl end groups. This design intended to avoid any interference of rhodamine B on biotin exposition on PMM surface, which is a key fundamental for cell trafficking studies. Biotin-decorated PMM were internalized more efficiently than non-targeted PMM in A549 lung cancer cells, while very low internalization was found in NHI3T3 normal fibroblasts. Biotin-decorated PMM entrapped NCL with good efficiency, displayed sustained drug release in protein-rich media and improved cytotoxicity in A549 cells as compared to free NCL (P<0.01). To go in depth into the actual therapeutic potential of NCL-loaded PMM, a cisplatin-resistant A549 lung cancer cell line (CPr-A549) was developed and its multidrug resistance tested against common chemotherapeutics. Free NCL was able to overcome chemoresistance showing cytotoxic effects in this cell line ascribable to nucleolar stress, which was associated to a significant increase of the ribosomal protein rpL3 and consequent up-regulation of p21. It is noteworthy that biotin-decorated PMM carrying NCL at low doses demonstrated a significantly higher cytotoxicity than free NCL in CPr-A549. These results point at NCL-based regimen with targeted PMM as a possible second-line chemotherapy for lung cancer showing cisplatin or multidrug resistance.

Hemocompatibility and ultrafiltration performance of PAN membranes surface-modified by hyperbranched polyesters

Maleic anhydride was grafted onto a polyacrylonitrile (PAN) membrane surface via ultraviolet irradiation. Then, hyperbranched polyester, with varying numbers of hydroxyl end-groups (H20, H30, and H40), was grafted onto the PAN membrane surface by the reaction of hydroxyl groups with anhydride groups of maleic anhydride. The modified membranes were characterized by scanning electron microscopy, static water contact angle, and attenuated total reflectance-Fourier transform infrared spectroscopy measurements. The modified membranes showed a higher water flux and better antifouling properties than pristine PAN membranes, and their hydrophilicity was significantly improved. Membrane biocompatibility was characterized by platelet adhesion, and the results indicate that the modified membranes exhibited good biocompatibility. Copyright © 2016 John Wiley & Sons, Ltd.

Superhydrophobic coatings with improved mechanical robustness based on polymer brushes

Abstract Superhydrophobic surfaces show great promise for applications that range from self-cleaning windows to anti-icing air-crafts. Practical applications require development of methods and materials for one-step fabrication of such coatings with sufficient mechanical robustness on large surface areas at low costs. Spray-coating of nanoparticles functionalized with low energy molecules can meet all these requirements except the challenges associated with the mechanical robustness of the coatings. Here, we demonstrate that the mechanical robustness of the spray-coated films can be improved by engineering the polymer matrix. Hydroxyl-terminated polystyrene (PS-OH) serves as a matrix for dispersing silica nanoparticles (12 nm) functionalized with fluorinated silanes. Hydroxyl ends of the PS-OH facilitate chemical and physical interactions with the underlying substrate, through grafting of polymer chains to form brushes and by presenting hydrophilic groups, respectively. The fabricated films showed a high level of surface roughness with water contact angles (θ) greater than 170°. The coatings retained their superhydrophobic behavior (θ > 150° and sliding angle

Synthesis of intracellular reduction-sensitive amphiphilic polyethyleneimine and poly(ε-caprolactone) graft copolymer for on-demand release of doxorubicin and p53 plasmid DNA

This study aims to present a new intelligent polymeric nano-system used for combining chemotherapy with non-viral gene therapy against human cancers. An amphiphilic copolymer synthesized through the conjugation of low molecular weight polyethyleneimine (LMw-PEI) and poly(ε-caprolactone) (PCL) via a bio-cleavable disulfide linkage was successfully employed for the simultaneous delivery of drug and gene molecules into target cells. Compared to the conventional PCL copolymerization pathway, this paper represents a straightforward and efficient reaction pathway including the activation of PCL-diol hydroxyl end groups, cystamine attachment and LMw-PEI conjugation which are successfully performed at mild conditions as confirmed by FTIR and 1H NMR. Thermal, morphological characteristics as well as biocompatibility of the copolymer were investigated. The copolymer showed great tendency to form positively charged nanoparticles (∼163.1nm, +35.3mV) with hydrophobic core and hydrophilic shell compartments implicating its potential for encapsulation of anti-cancer drug and plasmid DNA, respectively. The gel retardation assay confirmed that the nanoparticles could successfully inhibit the migration of pDNA at ∼5 nanoparticle/pDNAw/w. The in vitro cytotoxicity tests and LDH assay revealed that the cationic amphiphilic copolymer was essentially non-toxic in different carcinoma cell lines in contrast to branched PEI 25K. Moreover, the presence of redox sensitive disulfide linkages provided smart nanoparticles with on-demand release behavior in response to reducing agents such as cytoplasmic glutathione (GSH). Importantly, confocal microscopy images revealed that in contrast to free Dox, the nanoparticles were capable of faster internalizing into the cells and accumulating in the perinuclear region or even in the nucleus. Finally, the co-delivery of Dox and p53-pDNA using the copolymer displayed greater cytotoxic effect compared with the Dox-loaded nanoparticle counterpart as revealed by cell viability and Caspase 3 expression assay. These results suggest the copolymer as a promising candidate for the development of smart delivery systems. Statement of SignificanceWe employed cystamine dihydrochloride as a disulfide linkage for the conjugation of PCL diol and low molecular weight PEI segments through a straightforward and efficient reaction pathway at mild conditions. The new copolymer was essentially non-toxic in different carcinoma cell lines and showed great tendency to form positively charged nanoparticles. Therefore, it can be utilized as a promising platform for simultaneous drug and gene delivery to aggressive cancers. The results of drug and gene co-delivery experiments confirmed the pivotal role of disulfide linkage on the controlled release of both drug and gene molecules in response to glutathione concentration gradient between extracellular and intracellular microenvironments. In addition, the co-delivery of doxorubicin and p53 plasmid DNA using the new copolymer displayed greater cytotoxic effect compared with single agent (i.e. Dox) loaded counterpart, which indicated the significance of rapid dissociation of therapeutic agents from the carrier for synergistic cytotoxic effects on cancer cells.

Porous proton exchange membranes based on sulfonated poly (arylene ether ketone)/polylactide block copolymers for enhanced proton conductivity and dimensional stability

Sulfonated poly(arylene ether ketone) (SPAEK) with hydroxyl end group was synthesized and used as a precursor for the ring-opening polymerization of lactide to afford sulfonated poly(arylene ether ketone)/polylactide block copolymers. The proton exchange membranes based on the prepared block copolymers were fabricated by the solvent casting method for direct methanol fuel cell (DMFC) application. The pores with different average diameters from 50nm to 2.6μm were established by the selective removal of polylactide (PLA) molecules from the self-assembled copolymers in a variety of composition. The morphology of the prepared porous membranes was examined by scanning electron microscopy. A variety of membrane properties for DMFC application such as water uptake, dimensional swelling, thermal and mechanical stability, methanol permeability, and proton conductivity were investigated. Although the proton conductivity of the porous membranes was much higher than that of the non-porous ones at the same degree of sulfonation, it decreased with increasing pore size. In this study, the SPAEK with the smallest pore diameter of 50nm showed the highest proton conductivity and the lowest methanol permeability. The porous SPAEK membranes exhibited excellent mechanical and dimensional stability, although the water uptake was significantly increased by the presence of pores.

Functionalization and photocuring of an L-lactic acid macromer for biomedical applications

ABSTRACTL-lactic acid was the starting material for obtaining bioahesives. Reaction with 1,4-butanediol provided a telechelic lactic acid prepolymer with hydroxyl end groups further functionalized with 2-isocyanatoethyl methacrylate. Films were produced upon UV irradiation, 2 min, after addition of Irgacure 2959. This was a solvent and catalyst free process. Thermal characterization of films confirmed stability at physiological temperature, enabling photocuring. Adhesion properties were assessed with good results. In vitro degradation tests showed moderate hydrolytic instability dependent on thickness. SEM images revealed a uniform and compact structure. Thrombosis tests confirmed the materials’ thrombogenicity while biocompatibility experiments showed fibroblast viability and antimicrobial behavior.

Controlling polylactide stereocomplex (sc-PLA) self-assembly: From microspheres to nanoparticles

Linear and star-shaped polymers have been synthesized by the controlled ring-opening (ROP) polymerization of l- and d-lactide using 1-methyl-2-hydroxymethyl-3-butylimidazolium tetrafluoroborate and dipentaerythritol as initiators, respectively. To introduce carboxylic end-groups onto the star-shaped polylactides, the reaction of –OH end-groups with succinic anhydride was employed. Afterwards, the starting and modified polylactides were used for the preparation of star-shaped and star-shaped/linear stereocomplexes in 1,4-dioxane and tetrahydrofuran (THF). In these solvents, the stereocomplexes spontaneously precipitated. Star-shaped stereocomplexes with hydroxyl end-groups formed microspheres with diameters ranging from 1 to 4 μm (depending on the initial concentration of sc-PLA components) following precipitation from THF. However, the combined effect of the nature of the end-groups and PLA architecture causes the formation of uniform stereocomplex nanoparticles (∼400 nm) in 1,4-dioxane from the combination of star-shaped PLA functionalized with carboxylic end-groups and linear PLA with ionic liquid end-groups. Microscopic analysis showed that nanometre-sized grains of stereocomplexes (∼30 nm) aggregated to form larger stereocomplex nanoparticles. It was observed that the combination of three factors, i.e., the end-group interactions, architecture of the enantiomeric components, and basicity of the solvent in which the stereocomplexes are prepared, influences the properties and morphology of the final stereocomplex-based materials.

Fluorescent assay for alkaline phosphatase activity based on graphene oxide integrating with λ exonuclease

A novel fluorescence turn-on strategy for the alkaline phosphatase (ALP) assay is developed based on the preferential binding of graphene oxide (GO) to single-stranded DNA (ssDNA) over double-stranded DNA (dsDNA) coupled with λ exonuclease (λ exo) cleavage. Specifically, in the absence of ALP, the substrate-dsDNA constructed by one oligonucleotide with a fluorophore at the 3′-end (F-DNA) and its complementary sequence modified with a 5′-phosphoryl termini (p-DNA), is promptly cleaved by λ exo, and the resulting F-DNA is adsorbed on GO surface, allowing fluorescence quenching. Whereas the introduction of ALP leads to the hydrolysis of the P-DNA, and the yielding 5′-hydroxyl end product hampers the λ exo cleavage, inducing significant fluorescence enhancement due to the weak binding of dsDNA with GO. Under the optimized conditions, the approach exhibits high sensitivity and specificity to ALP with a detection limit of 0.19 U/L, and the determination of ALP in spiked human serum samples has also been realized. Notably, this new approach not only provides a novel and sensitive platform for the ALP activity detection but also promotes the exploitation of the GO-based biosensing for the detection of the protein with no specific binding element, and thus extending the GO-based sensing applications into a new field.

Pyrazole Supported Zinc(II) Benzoates as Catalysts for the Ring Opening Copolymerization of Cyclohexene Oxide and Carbon Dioxide

The bis(pyrazole)zinc(II) benzoate complexes bis(3,5-diphenylpyrazole)zinc(II) benzoate (1), bis(3,5-diphenylpyrazole)zinc(II) 3,5-dinitrobenzoate (2), bis(3,5-diphenylpyrazole)zinc(II) 4-hydroxybenzoate (3), and bis(3,5-di-tert-butylpyrazole)zinc(II) 2-chlorobenzoate (4) were synthesized from the reaction of 3,5-diphenylpyrazole (L1) or 3,5-di-tert-butylpyrazole (L2), zinc(II) acetate and the appropriate benzene carboxylic acid. The molecular structure of complex 2 confirmed that these zinc(II) benzoate complexes adopt a 4-coordinate tetrahedral geometry. All four complexes were screened as catalysts for the copolymerization of carbon dioxide (CO2) and cyclohexene oxide (CHO) and were found to be active for the formation of poly(cyclohexene carbonate) (PCHC) at CO2 pressures as low as 1.0 MPa under solvent-free conditions and without the use of a co-catalyst. At some reaction condition, most of the catalysts produced PCHC with high carbonate content of up to 98% and a good amount of cyclic cyclohexene carbonate (CCHC). The copolymers produced have low to moderate molecular weights (5200–12300 g/mol) and with polydispersity indices that vary from 1.19 to 2.50. Matrix Assisted Laser Desorption/Ionization-Time of Flight Mass Spectra (MALDI-TOF MS) of these copolymers showed they have benzoate and hydroxyl end groups.

Preparation and characterization of an oxygen permselective polydimethylsiloxane hollow fibre membrane

Simple preparation of a polydimethylsiloxane (PDMS) hollow fibre air separation membrane by a condensation reaction between the hydroxyl-end groups and hydride groups of polysiloxane reactants over a porous hollow fibre support.

Perfluoroalkylated linear polyglycerols and their supramolecular assemblies in aqueous solution

In this study, amphiphiles composed of linear polyglycerols (LPGs) with hydroxyl, methoxy, and ethoxy side groups and end capped with one or two perfluorooctyl chains (Rf8) have been designed to form supramolecular architectures.

The role of H-bonds in the solid state organization of [1]benzothieno[3,2-b][1]benzothiophene (BTBT) structures: bis(hydroxy-hexyl)-BTBT, as a functional derivative offering efficient air stable organic field effect transistors (OFETs)

The rapid and inexpensive functionalization of the BTBT core with hydroxyl end group functionalized hexyl chains offered a new platform for functionalized self-organising BTBT.

イオン結合末端を有する極薄膜PFPE潤滑剤のDLC表面への吸着特性

Affinity to DLC surface of two types of PFPE lubricant films were compared. One lubricant material (SNH2) was Deminaum main-chain with single ionic end-group and other lubricant material (Z-tetraol) was Fomblin main-chain with double hydroxyl end-groups. SNH2 showed much thicker lubricant thickness than Z-tetraol at the same lubricant concentration. However, SNH2 showed larger polar surface energy than Z-tetraol. The reason was estimated that the ionic function had stronger polarity and that polarity increased the polar surface energy.

Ordered self-assembled monolayers terminated with different chemical functional groups direct neural stem cell linage behaviours

Neural stem cells (NSCs) have been a promising candidate for stem cell-based nerve tissue regeneration. Therefore, the design of idea biomaterials that deliver precise regulatory signals to control stem cell fate is currently a crucial issue that depends on a profound understanding of the interactions between NSCs with the surrounding micro-environment. In this work, self-assembled monolayers of alkanethiols on gold with different chemical groups, including hydroxyl (−OH), amino (−NH2), carboxyl (−COOH) and methyl (−CH3), were used as a simple model to study the effects of surface chemistry on NSC fate decisions. Contact angle measurement and x-ray photoelectron spectroscopy (XPS) examination implied that all types of alkanethiols self-assembled on gold into a close-packed phase structure with similar molecular densities. In this study, we evaluated NSC adhesion, migration and differentiation in response to different chemical functional groups cultured under serum-free conditions. Our studies showed that NSCs exhibited certain phenotypes with extreme sensitivity to surface chemical groups. Compared with other functional groups, the SAMs with hydroxyl end-groups provided the best micro-environment in promoting NSC migration and maintaining an undifferentiated or neuronal differentiation state. −NH2 surfaces directed neural stem cells into astrocytic lineages, while NSCs on −COOH and −CH3 surfaces had a similar potency to differentiate into three nerve lineages. To further investigate the possible signaling pathway, the gene expression of integrin β1 and β4 were examined. The results indicated that a high expression of β1 integrin would probably have a tight correlation with the expression of nestin, which implied the stemness of NSCs, while β4 integrin seemed to correspond to the differentiated NSCs. The results presented here give useful information for the future design of biomaterials to regulate the preservation, proliferation and differentiation of NSCs for central nervous tissue engineering.

Studying the effect of hyperbranched polymer modification on the kinetics of curing reactions and physical/mechanical properties of UV-curable coatings

Abstract A polyester-amide based hyperbranched polymer with hydroxyl end-groups is modified by the aid of acrylic functionalities. Two levels of modification, i.e. 40% and 65%, are considered. The unmodified hyperbranched polymer and the modified ones are added to UV-curable monomeric and oligomeric systems. Rheology measurements are conducted to investigate the effects of hyperbranched polymer on the rheological behavior. In order to assess the curing kinetics and physical/mechanical characteristics of the samples, photo-DSC and DMA experiments are exploited, respectively. The effect of viscosity and number of UV-curable functionalities of the hyperbranched polymer on the curing level and kinetics of the curing reactions are discussed. Dynamic mechanical analysis shows that the addition of hyperbranched polymer in the formulation increases a 25% in storage modulus of the glassy region and cross-linking density of the UV-curable coating. Furthermore, it is also seen that the existence of the hyperbranched polymer increases the viscosity of Trimethylolpropane triacrylate (TMPTA)-based system while it is decreasing the viscosity of oligomeric-based of the epoxy di-acrylate system. It is obtained that the hyperbranched polymer makes the curing level in the monomeric and the oligomeric system, improve up to 15% and 10% correspondingly. It is also observed that T g s of the coatings containing the hyperbranched polymer increases up to 5.9 °C.