Synthesis of oligo(ethylene glycol) methacrylate polymer brushes

Here we report a study into controlling the polymerization of mono-hydroxy and mono-methoxy terminated oligo(ethylene glycol) methacrylates (HOEGMA and MeOEGMA, respectively) from functionalised, planar surfaces via atom transfer radical polymerization (ATRP). The effects of initiator structure, initiator density, temperature, and monomer ratios have been investigated for these polymerizations. The polymer brushes grown in this way were found to convey protein resistance to the underlying inorganic substrates, prone to facile protein adsorption in their native state.     

Preparation of thermo- and redox-responsive branched polymers composed of three-armed oligo(ethylene glycol)

We herein report the preparation of thermo- and redox-responsive branched polymers by the condensation reaction of three-armed oligo(ethylene glycol) (trisOEG) and cystamine (CA). The prepared branched polymers exhibited a soluble–insoluble transition at a lower critical solution temperature (LCST) and formed coacervate droplets through a liquid–liquid phase separation process. We then demonstrated control of the LCSTs of the branched polymers by varying the feed ratio of CA and the surrounding salt concentration close to body temperature. In addition, the trisOEG-cys _x polymer formed coacervate droplets above the LCST, in which hydrophobic molecules were condensed. The redox response of the branched polymers was also investigated. Interestingly, the branched polymers degraded to low-molecular-weight materials (i.e., trisOEG) in the presence of dithiothereitol as a reducing agent through cleavage of the disulfide bond of CA. This facile preparation of branched polymers is expected to be valuable in the context of functional biomedical materials and modifiers for materials surfaces, such as the bases for drug delivery carriers and separation materials. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 2623–2629     

(Co)polymers of oligo(ethylene glycol) methacrylates—temperature‐induced aggregation in aqueous solution

The synthesis and aggregation behavior of well‐defined thermosensitive (co)polymers of oligo(ethylene glycol) methacrylates (POEGMA) in aqueous solutions were investigated. The cloud points of the POEGMAs solutions were determined by turbidimetry and dynamic light scattering. For POEGMA (co)polymers the cloud point temperature (T_CP) increased linearly with increasing content of more hydrophilic comonomer. The mesoglobules formed by POEGMAs in dilute aqueous solutions above T_CP were studied by light scattering. The size of mesoglobules depended on the concentration and the heating procedures. The aggregates became smaller with decreasing initial concentration of polymer and increasing rates of temperature change. By selecting the proper heating and dilution procedures, the influence of the (co)polymer structure on the size of the mesoglobules could be determined. The size of the mesoglobules decreased with the length of the OEG side chains and increased with increasing content of more hydrophilic comonomer. The light scattering parameters of the mesoglobules—A₂ values and shape factors ${R_{\rm g}\over R_{\rm h}}$ —suggested that the hydrophilic OEG side chains placed at the periphery of the mesoglobules in direct contact with the surrounding water controlled the size of mesoglobules and their stability. Shape factors for all POEGMA mesoglobules indicated that the mesoglobules remained highly hydrated after formation. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

New Poly(propylene glycol)‐ and Poly(ethylene glycol)‐Based Polymer Gelators with L‐Lysine

Summary: New polymer gelators consisting of poly(propylene glycol) or poly(ethylene glycol) and L ‐lysine‐based low‐molecular‐weight gelators have been developed. These polymer gelators were synthesized according to a simple procedure with high reaction yield, and formed organogels in many organic solvents. The organogelation mechanism was proposed from the transmission electron microscopy and FTIR spectroscopy studies.

Structures of the polymer gelators synthesized here.     

Thermoresponsive gene carriers based on polyethylenimine-graft-poly[oligo(ethylene glycol) methacrylate

A family of thermoresponsive cationic copolymers (TCPs) that contain branched PEI 25 K as the cationic segment and poly(MEO(2)MA-co-OEGMA(475)) as the thermosensitive block (TP) is prepared. The DNA binding capability, physicochemical properties, and biological performance of the TCPs are studied. All of these TCPs can condense DNA to form polyplexes with diameters of 150-300 nm and zeta potentials of 7-32 mV at N/P ratios between 12 and 36. The length of TP block is a key factor for shielding the positive surface charge of the polyplexes and protecting them against protein adsorption. TCPs with a higher TP content have a lower cytotoxicity while the best transfection performance is achieved by the TCPs with longest TP length, reaching a level of the intact PEI 25 K in the presence of serum.     

Revealing the effect of oligo(ethylene glycol) side chains on n-doping process in FBDPPV-based polymers

The low doping efficiency of n-doped systems limits the development of n-type organic conducting materials. Oligo(ethylene glycol) (OEG) as the flexible chain in conjugated small molecules and polymers may improve doping efficiency. However, OEG side chains also bring unexpected low mobility and poor film morphology. Herein, we propose the stronger solution-state aggregation plays a dominated role in charge transport and morphology of OEG-substituted polymer. The solution-state aggregation also affects doping process. Therefore, we develop a series of polymers based on 3,7-bis((E)-7-fluoro-1-(2-octyldodecyl)-2-oxoindolin-3-ylidene)-3,7-dihydrobenzo[1,2-b:4,5-b']difuran-2,6-dione (FBDPPV) with different ratios of OEG side chain to investigate the effect of side chain on solution-state aggregation and n-doping process. After n-doped by hexahydro-1H,3a1H,4H,7H-3a,6a,9a-triazaphenalene (TAM), FBDPPV with 50% OEG affords the highest doping efficiency and conductivity, while FBDPPV with 100% OEG shows lower conductivity. Combination of ultraviolet–visible–near infrared absorption spectra, grazing-incidence wide-angle X-ray scattering and atomic force microscopy, we reveal that serious aggregated extent in solution of OEG-substituted polymer result in phase separation and rough morphology, which are the origins of poor conductivity. Our work provides a new perspective on the effect of the OEG side chain on the doped polymer systems, suggesting suitable solution-state aggregation is crucial to high doping efficiency and high conductivity.     

Thermosensitivity of Bile Acid‐Based Oligo(ethylene glycol) Stars in Aqueous Solutions

Amphiphilic star‐shaped oligo(ethylene glycol)s with a hydrophobic bile acid core and varying number of hydrophilic arms have been made. Their thermal behavior in aqueous solutions depends on the number rather than the length of the arms. The two‐armed lithocholate derivative showed the strongest tendency for association and exhibited the lowest cloud point (79 °C) of the oligomers made, as well as another phase separation at a lower temperature (31 °C). The “double thermosensitivity” arising both from the salt‐dependent LCST of the oligo(ethylene glycol) segments and the temperature‐responsive self‐assembly of amphiphilic bile acid derivative provides an interesting path in the design of bile acid‐based smart materials.

     

Selective enrichment with “click oligo (ethylene glycol)” column and TOF–MS characterization of simple phenylpropanoids in the fruits of Forsythia suspensa

To separate samples of complex natural products, highly efficient and selective separation methods should be developed. Herein, a selective enrichment method was developed to separate Forsythia suspensa components with “click oligo (ethylene glycol)” (OEG) column in reversed phase (RP) mode. In this method, F. suspensa aqueous extract was successfully separated. And three fractions with structure‐related compounds were obtained. Fraction I mainly consisted of C₆–C₂ natural alcohols and glycosides, fraction II mostly consisted of lignans, and fraction III mainly consisted of simple phenylpropanoids (SP). Then, the three fractions were separated with ultra‐performance liquid chromatography (UPLC). Four more lignans were observed in fraction II, and eight more SP were observed in fraction III than that without OEG column. Fraction III was successively characterized by TOF–MS, 2 acids (caffeic acid and chlorogenetic acid), 26 SP with caffeoyl, and 2 SP with coumaroyl were characterized. The results prove that a valid method has been developed to selectively enrich SP and lignans. And the method combined with UPLC can efficiently separate SP and lignans. Furthermore, the TOF–MS method is effective to confirm the substituents of SP.     

Methoxy poly(ethylene glycol)‐b‐poly(octadecanoic anhydride)‐b‐methoxy poly(ethylene glycol) amphiphilic triblock copolymer nanoparticles as delivery vehicles for paclitaxel

A series of amphiphilic triblock copolymers, methoxy poly(ethylene glycol)‐b‐poly(octadecanoic anhydride)‐b‐methoxy poly(ethylene glycol) (mPEG‐b‐POA‐b‐mPEG), were prepared via melt polycondensation of methoxy poly(ethylene glycol) (mPEG) and poly(octadecanoic anhydride) (POA). mPEG‐b‐POA‐b‐mPEG were characterized by FTIR, ¹H‐NMR, GPC, DSC, and XRD. Drug‐loaded mPEG‐b‐POA‐b‐mPEG nanoparticles (NPs) with spherical morphology and narrow size polydispersity index were prepared by nanoprecipitation technique with paclitaxel as the model drug. In vitro release behaviors of drug‐loaded NPs present that the biphasic process and the release mechanism of each phase are zero order drug releases. According to this study, mPEG‐b‐POA‐b‐mPEG NPs could serve as suitable delivery agents for paclitaxel and other hydrophobic drugs. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and characterization of light‐emitting oligo(p‐phenylene‐vinylene)s and polymeric derivatives containing three‐ and five‐conjugated phenylene rings

Several series of light‐emitting oligo(p‐phenylene‐vinylene)s (BIII and BV series containing three‐ and five‐conjugated phenylene rings) with various side groups and end groups attached to the cores were synthesized and characterized. The analogous PBV polymers, derived from the BV series, were also synthesized and investigated. Blue and greenish light emissions were observed in the photoluminescence (PL) and electroluminescence (EL) spectra of the blend and pure films with these π‐conjugated structures. In contrast to the three‐conjugated ring oligomers, the five‐conjugated ring derivatives (oligomers and polymers) had larger maximum emission wavelength values of PL and EL emissions. Mesomorphism was introduced into the BV series by the replacement of three‐conjugated rings (BIII series) with five‐conjugated phenyl cores (BV series). The liquid‐crystalline properties of the BV series with end groups (on both end rings) were better than those of analogous BV‐OC₈ without end groups. Polarized PL emissions were obtained by the alignment of liquid‐crystalline phase in rubbing cells. Upon heating, different PL emission wavelengths and intensities were observed in various phases. Not only the solubility and thermal properties but also the PL and EL properties could be effectively adjusted by the attachment of flexible alkoxy groups either on the central rings or on both end rings of the conjugated cores. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 783–800, 2006     

Novel electron-deficient oligo(phenyleneethynylene) derivatives for molecular electronics

This work reports synthesis and characterizations of two new electron-poor “oligo(phenyleneethynylene) (OPE) type” molecular wires for fundamental studies of electron transport in molecular junctions. These OPE derivatives display three aromatic rings functionalized (i) with NO₂ (OPN) or fluorine (OPF) groups on the central aryl core and (ii) with the requisite protected thiolate anchoring groups on the lateral rings at both ends. We show that the moderately effective Sonogashira couplings can give access to such rare electrodeficient molecules but are unfortunately associated with significant side reactions. We detail the choice of adequate reaction conditions to allow the recovery of suitable amounts of compounds bearing several strongly electron-withdrawing substituents on their central ring for further study of the physical properties.     

Micellization and Thermogelation of Poly(ether urethane)s Comprising Poly(ethylene glycol) and Poly(propylene glycol)

A series of multiblock poly(ether urethane)s comprising poly(ethylene glycol) (PEG), and poly(propylene glycol) (PPG) segments were synthesized. Their aqueous solutions exhibited thermogelling behavior at critical gelation concentrations (CGC) ranging from 8 to 12 wt%. The composition and structural information of the copolymers were studied by GPC and ¹H NMR. The critical micellization concentration (CMC) and thermodynamic parameters for micelle formation were determined at different temperatures. The temperature response of the copolymer solutions were studied and found to be associated with the composition of the copolymers.     

Novel synthesis of biodegradable star poly(ethylene glycol)‐block‐poly(lactide) copolymers

Biodegradable star‐shaped poly(ethylene glycol)‐block‐poly(lactide) copolymers were synthesized by ring‐opening polymerization of lactide, using star poly(ethylene glycol) as an initiator and potassium hexamethyldisilazide as a catalyst. Polymerizations were carried out in toluene at room temperature. Two series of three‐ and four‐armed PEG‐PLA copolymers were synthesized and characterized by gel permeation chromatography (GPC) as well as ¹H and ¹³C NMR spectroscopy. The polymerization under the used conditions is very fast, yielding copolymers of controlled molecular weight and tailored molecular architecture. The chemical structure of the copolymers investigated by ¹H and ¹³C NMR indicates the formation of block copolymers. The monomodal profile of molecular weight distribution by GPC provided further evidence of controlled and defined star‐shaped copolymers as well as the absence of cyclic oligomeric species. The effects of copolymer composition and lactide stereochemistry on the physical properties were investigated by GPC and differential scanning calorimetry. For the same PLA chain length, the materials obtained in the case of linear copolymers are more viscous, whereas in the case of star copolymer, solid materials are obtained with reduction in their T_g and T_m temperatures. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3966–3974, 2007     

Biocompatibility evaluation of self‐assembled micelles prepared from poly(lactide‐co‐glycolide)‐poly(ethylene glycol) diblock copolymers

In this work, a series of PLGA‐PEG diblock copolymers were synthesized by ring‐opening polymerization of L‐lactide and glycolide using mPEG as macroinitiator and stannous octoate as catalyst. Spherical micelles were obtained from the various copolymers by using co‐solvent evaporation method. The biocompatibility of micelles was evaluated with the aim of assessing their potential in the development of drug delivery systems. Various aspects of biocompatibility were considered, including MTT assay, agar diffusion test, release of cytokines, hemolytic test, dynamic clotting time, protein adsorption in vitro, and zebrafish embryonic compatibility in vivo. The combined results revealed that the micelles present good cytocompatibility and hemocompatibility in vitro. Moreover, the cumulative effects of micelles throughout embryos developing stages have no toxicity in vivo. It is thus concluded that micelles prepared from PLGA‐PEG copolymers present good biocompatibility as potential drug carrier.     

Side‐chain crystallization behavior of graft copolymers consisting of amorphous main chain and crystalline side chains: Poly(methyl methacrylate)‐graft‐poly(ethylene glycol) and poly(methyl acrylate)‐graft‐poly(ethylene glycol)

Graft copolymers consisting of amorphous main chain, poly(methyl methacrylate) (PMMA), or poly(methyl acrylate) (PMAc), and crystalline side chains, poly(ethylene glycol) (PEG), have been prepared by copolymerization of PEG macromonomers with methyl methacrylate or methyl acrylate (MMAx or MACx, respectively). Because of the compatibility of PMMA/PEG and PMAc/PEG, from small‐angle X‐ray scattering results, the main and side chains in graft copolymers were suggested to be homogeneous in the molten state. Differential scanning calorimetry (DSC) cooling scans revealed that PEG side chains for graft copolymers with large PEG fractions were crystallized when the sample was cooled, with a cooling rate of 10 °C/min. The spherulite pattern observed by a polarized optical microscope suggested the growth of PEG crystalline lamellae. Crystallization of PEG in MMAx was more restrained than in MACx. From these results, we have concluded that the crystallization behavior of the grafted side chains is strongly influenced by the glass transition of a homogeneously molten sample as well as dilution of the crystallizable chains. Domain spacings for isothermally crystallized graft copolymers were described by interdigitating chain packing in crystalline–amorphous lamellar structure. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 79–86, 2005     

Synthesis and non‐isothermal crystallization kinetics of poly(ethylene terephthalate)‐co‐poly(propylene glycol) copolymers

Poly(ethylene terephthalate)‐co‐poly(propylene glycol) (PET‐co‐PPG) copolymers with PPG ratio ranging from 0 to 0.90 mol% were synthesized by the melt copolycondensation. The intrinsic viscosity, structure, non‐isothermal crystallization behavior, nucleation and spherulitic growth of the copolymers were investigated by Ubbelohde viscometer, Proton Nuclear Magnetic Resonance (¹H‐NMR), differential scanning calorimetry, and polarized optical microscopy, respectively. The non‐isothermal crystallization process of the copolymers was analyzed by Avrami, Ozawa, Mo's, Kissinger, and Dobreva methods, respectively. The results showed that the crystallizability of PET was apparently enhanced with incorporating a small amount of PPG, which first rose and then reduced with increasing amount of PPG in the copolymers at a given cooling rate. The crystallization mechanism was a three‐dimensional growth with both instantaneous and sporadic nucleation. Particularly, PET‐co‐PPG containing 0.60 mol% PPG exhibited the highest crystallizability among all the copolymers. Copyright © 2015 John Wiley & Sons, Ltd.     

Poly(ethylene glycol)‐block‐Poly(glycidyl methacrylate) with Oligoamine Side Chains as Efficient Gene Vectors

Well‐defined diblock copolymers, poly(ethylene glycol)‐block‐poly(glycidyl methacrylate)s (PEG‐b‐PGMAs), with different poly(glycidyl methacrylate) (PGMA) chains, were prepared via atom transfer radical polymerization (ATRP) from the same macromolecular initiator 2‐bromoisobutyryl‐terminated poly(ethylene glycol) (PEG). Ethyldiamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and polyethyleneimine (PEI) with an of 400 (PEI₄₀₀) were used to decorate PEG‐b‐PGMAs to get the cationic polymers PEG‐b‐PGMA‐ oligoamines. These cationic polymers possessed high buffer capability and could condense plasmid DNA (pDNA) into nanoscaled complexes of 125–530 nm. These complexes showed the positive zeta potential of 20–35 mV at N/P ratios of 10–50. Most of them exhibited very low cytotoxicity and good transfection efficiency in 293T cells. The presence of the serum medium did not decrease the transfection efficiency due to the steric stabilization of the PEG chains.

     

Purification of compounds from Lignum Dalbergia Odorifera using two-dimensional preparative chromatography with Click oligo (ethylene glycol) and C18 column

Purification of compounds from traditional Chinese medicines (TCMs) is an important task for understanding the chemical composition of TCMs. However, it is difficult to obtain compounds with high enough purity for identification by NMR due to the complexity of TCMs in chemical composition. In this study, a two‐dimensional purification method based on a Click oligo (ethylene glycol) column and a C18 column was developed to realize an orthogonal separation in preparative level for purifying compounds efficiently. The first dimensional preparation was performed on a Click oligo (ethylene glycol) column to simplify the sample into the fractions with good separation repeatability. On the first dimension, 7.2 g sample was separated into 11 fractions with a recovery of 86% within 6 h. A C18 column was taken as the second dimension to realize the high‐performance separation and rapid preparation from the fractions collected from the first dimension. Eight compounds in fraction 6 and 2 compounds in fraction 8 were isolated and identified after optimizing the separation and collection parameters. This method is a high‐efficient and orthogonal preparation method to improve the separation of a complex sample and increase the purity of the compounds, which benefits from the application of novel materials in the preparation and purification.     

Libraries of methacrylic acid and oligo(ethylene glycol) methacrylate copolymers with LCST behavior

Homopolymers of methacrylic acid (MAA), monoethyleneglycol methyl ether methacrylate (MEOMA), diethyleneglycol methyl ether methacrylate (MEO₂MA), oligo(ethyleneglycol) methyl ether methacrylate (OEGMA₄₇₅ and OEGMA₁₁₀₀) and oligo(ethyleneglycol) ethyl ether methacrylate (OEGEMA₂₄₆) were synthesized with various chain lengths via reversible addition fragmentation chain transfer (RAFT) polymerization. The homopolymers of MAA, MEOMA and OEGMA₁₁₀₀ did not show any cloud point (CP) in the range of 0–100 °C, whereas at a pH value of 7, the CPs were found to be 20.6, 93.7, and 20.0 °C for p(MEO₂MA), p(OEGMA₄₇₅) and p(OEGEMA₂₄₆), respectively, with an initial monomer to initiator ratio of 50. Furthermore, statistical copolymer libraries of MAA with OEGMA₄₇₅ and OEGMA₁₁₀₀ were prepared. The cloud points of the random copolymers of MAA and OEGMA₄₇₅ were found to be in the range of 20–90 °C; surprisingly, even though the homopolymers of MAA and OEGMA₁₁₀₀ did not exhibit any LCST behavior, the copolymers of these monomers at certain molar ratios (up to 40% OEGMA₁₁₀₀) revealed a double responsive behavior for both temperature and pH. Finally, the cloud points were found to be in the range of 22–98 °C, measured at pH values of 2, 4, and 7, while no cloud point was detected at pH 10. © Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7138–7147, 2008