Synthesis and characterizations of a novel zwitterionic hybrid copolymer containing both sulfonic and carboxylic groups via sulfonation and zwitterionic process

A novel zwitterionic hybrid copolymer containing both sulfonic and carboxylic groups was synthesized via sulfonation, zwitterionic process and sol-gel reaction. The properties of the step products were characterized by FT-IR spectra, thermal analyses, MALDI measurements and SEM morphologies. FT-IR spectra confirmed the related reactions. TGA and DrTGA analyses showed that their thermal stability enhanced with an increase in the zwitterionic extent. DSC curves revealed that both the glass transition temperature and the melting temperature elevated with the rising content of ion pairs. MALDI measurements suggested that the molecular structure of the zwitterionic hybrid PEG-[Si(OEt)₃]₂SO₃HCOOH was more stable than that of neutral hybrid PEG-[Si(OEt)₃]₂ or that of negatively charged hybrid PEG-[Si(OEt)₃]₂SO₃H. SEM image of the sulfonated polymer film indicated that the pore size was within 2.4-6.1 μm; whereas SEM of the zwitterionized copolymer film displayed that its pore size was less than 1 μm. This shrinkage in pore size can be ascribed to the introduction of carboxylic groups into the copolymer chains. Compared with that observed in the unionized polymer film, the large difference in the morphology of the ionized copolymer films demonstrated that ionization could alter these copolymer’s characteristics. Due to its excellent pore-creating performance, this zwitterionic hybrid copolymer expects to be employed to prepare nanofiltration and ultrafiltration membranes.     

Sol-gel preparation and properties of interpenetrating, encapsulating and blend silica-based urea-formaldehyde hybrid composite materials

Four different silica-based urea-formaldehyde (UF/SiO₂) composite materials were prepared by various sol-gel synthetic procedures to yield an interpenetrating (IPN-UF/SiO₂), a micro-size UF resin encapsulated inside silica shell (Encap-UF/SiO₂), a micro-size silica encapsulated inside UF shell (Encap-SiO₂/UF), and a blend mixture (Blend-UF/SiO₂) hybrid systems. The thermal properties of the obtained organic-inorganic hybrid composite materials were examined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The structure and morphology of the obtained systems were investigated by infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Their surface porosity and acidity were evaluated from the nitrogen adsorption isotherm and the pH of the corresponding 10% aqueous suspension, respectively. All the results provided evidence for the formation of different hybrid systems with different surface, structural and morphological characteristics.     

Synthesis of polypeptide/inorganic hybrid block copolymers

Polypeptide/inorganic hybrid copolymers were obtained by a four-step synthetic approach combining (i) atom transfer polymerization of tert-butyl acrylate, (ii) chemical modification of the bromo end groups of ATRP-polymers into primary amino group using Gabriel reaction, (iii) ring opening polymerization of N_ε-trifluoroacetyl-l-lysine or γ-benzyl-l-glutamate N-carboxyanhydrides followed by (iv) the transamidification reaction using a large excess of (3-aminopropyl)trimethoxysilane to substitute the tert-butyl groups of the poly(tert-butyl acrylate) block. Products were characterized using ¹H NMR, FT-IR, DSC and MALDI-TOF MS. These techniques proved that polymerization of tert-butyl acrylate was controlled whatever the molecular weight targeted and that bromide was quantitatively converted to amino end group by a original method leading to the synthesis of copolymers in the presence of N-carboxyanhydrides as monomers. Amphiphilic polypeptide/inorganic hybrid copolymers were then achieved.     

Synthesis and thermal properties of hybrid copolymers of syndiotactic polystyrene and polyhedral oligomeric silsesquioxane

Copolymerizations of styrene and the polyhedral oligomeric silsesquioxane (POSS)–styryl macromonomer 1‐(4‐vinylphenyl)‐3,5,7,9,11,13,15‐heptacyclopentylpentacyclo [9.5.1.1^3,9.1^5,15.1^7,13] octasiloxane have been performed with CpTiCl₃ in conjunction with methylaluminoxane. Random copolymers of syndiotactic polystyrene (sPS) and POSS have been formed and fully characterized with ¹H and ¹³C NMR, gel permeation chromatography, differential scanning calorimetry, and thermogravimetric analysis. NMR data reveal a moderately high syndiotacticity of the polystyrene backbone consistent with this use of CpTiCl₃ as a catalyst and POSS loadings as high as 24 wt % and 3.2 mol %. Thermogravimetric analysis of the sPS–POSS copolymers under both nitrogen and air shows improved thermal stability with higher degradation temperatures and char yields, demonstrating that the inclusion of the inorganic POSS nanoparticles makes the organic polymer matrix more thermally robust. The polymerization activity and thermal stability are also compared with those of reported atactic polystyrene–POSS copolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 885–891, 2002; DOI 10.1002/pola.10175     

An internal doping method for the preparation of transparent hybrid xerogels containing nano-sized iron particles

Sol-gel copolymerization of iron tricarbonyl-2-(triisopropoxysilyl)-1,3-butadiene with 1,6-bistriethoxysilylhexane and 1,4-bistriethoxysilylbenzene followed by drying produced bridged polysilsesquioxane xerogels. These porous, transparent hybrid materials containing the iron metal precursor were irradiated (UV) and heated under vacuum resulting in the deposition of nano-sized iron particles doped in the xerogels. EDAX and electron diffraction techniques were used to characterize the iron phases. The TEM images of these doped xerogels provided additional information regarding the domain size of the iron phase.Using a combination of external doping of Cd²⁺ and S^2– ions and internal doping of Fe°, mixed Fe/CdS phases were prepared within the porous bridged polysilsesquioxane xerogels. The resulting doped xerogels were found to have retained their porous morphology.     

Simple synthesis of zwitterionic diblock copolymers for the application on metal nanoparticles preparation

AB diblock copolymers of poly(2-(dimethylamino)ethyl metharylate-block-potassiurn acrylate) were prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization. The structure of the block polymer was determined by the nuclear magnetic resonance (NMR) spectroscopy and the gel permeation chromatography. Moreover, it has also been shown that the diblock copolymers exhibit aggregate as function of the pH according to the result of ¹H-NMR spectroscopy, FT-IR absorption spectra, UV-vis transmittance spectroscopy, transmission electron microscopy and ultrasonic particle size analyzer. The result was attributed that such AB diblock copolymers were tailored to undergo pH-induced self-assembly. Furthermore, the aggregate can be as template of metal nanoparticles preparation, and the sizes of the aggregate, in turn, strongly control nanoparticle sizes.     

Novel vesicles self-assembled from amphiphilic star-armed PEG/polypeptide hybrid copolymers for drug delivery

A novel amphiphilic four‐armed [poly(ε‐benzyloxycarbonyl‐L ‐lysine)]₂‐block‐poly(ethylene glycol)‐block‐[poly(ε‐benzyloxycarbonyl‐L ‐lysine)]₂ hybrid copolymer has been prepared. The cytotoxicity study shows that the copolymer has good biocompatibility with no obvious inhibition effect on cell growth. The amphiphilic copolymers could self‐assemble to form vesicles in aqueous solution. DOX · HCl, as a hydrophilic drug, can be loaded into the vesicles, and then successfully internalized by human breast cancer MCF‐7 cells. Importantly, the DOX‐loaded vesicles show a greatly improved drug release behavior with a zero‐order release at the initial stage, suggesting a great potential as the carrier of hydrophilic drugs for controlled drug delivery.

     

The maleimide modified epoxy resins for the preparation of UV‐curable hybrid coatings

In the present study, maleimide‐modified epoxide resin containing UV‐curable hybrid coating materials were prepared and coated on polycarbonate substrates in order to improve their surface properties. UV‐curable, bismaleimide‐modified aliphatic epoxy resin was prepared from N‐(p‐carboxyphenyl) maleimide (p‐CPMI) and cycloaliphatic epoxy (Cyracure‐6107) resin. The structure of the bismaleimide modified aliphatic epoxy resin was analyzed by FTIR and the characteristic absorption band for maleimide ring was clearly observed at 3100 cm^?1. Silica sol was prepared from tetraethylorthosilicate (TEOS) and methacryloxy propyl trimethoxysilane (MAPTMS) by sol–gel method. The coating formulations with different compositions were prepared from UV‐curable bismaleimide‐based epoxy oligomer and sol–gel mixture. The molecular structure of the hybrid coating material was analyzed by ²⁹Si‐CP/MAS NMR spectroscopy techniques. In the ²⁹Si CP/MAS NMR spectrum of the hybrid coating, mainly two kinds of signals were observed at ?68 and ?110 ppm that correspond to T³ and Q⁴ peaks, respectively. This result shows that a fully condensed structure was obtained. The thermal and morphological properties of these coatings materials were investigated by using TGA and SEM techniques. Hardness and abrasion resistance properties of coating materials were examined and both were found to increase with sol–gel precursor content of the coating. The photopolymerization kinetics was investigated by using RT‐IR. 70% conversion was attained with the addition of 15 wt% of BMI resin into the acrylate‐based coating formulation. It was found that the UV‐curable organic–inorganic hybrid coatings improved the surface properties of polycarbonate. Copyright © 2009 John Wiley & Sons, Ltd.     

Study on the moisture absorption of zwitterionic copolymers for moisture‐sensitive shape memory applications

This study develops a new type of moisture‐sensitive shape memory polymer based on zwitterionic copolymers synthesized with acrylic acid (AA) and 3‐Dimethyl (methacryloyloxyethyl) ammonium propane sulfonate (DMAPS). The moisture absorption properties of zwitterionic copolymers are particularly investigated in this paper. The results demonstrate that the DMAPS/AA copolymers possess a sulfobetaine structure and form a two‐phase separation structure. The zwitterionic copolymers show both good hydrophilic properties and moisture absorption properties. Both AA and DMAPS segments influence the hydrophilic properties and moisture absorption of the composite copolymer. The moisture absorption process is well modeled by Fick's second law in its initial stage. The moisture absorption is mainly determined by immersion conditions and the given materials' structure. Moisture absorption speed and saturated moisture absorption both increase with an increase in DMAPS content as well as the immersion temperature. The increased moisture absorption rate and higher saturated moisture absorption results from the higher activation energy of diffusion. The DMAPS/AA copolymers demonstrate adequate moisture‐sensitive shape memory effects. Stain recovery is faster in the zwitterionic copolymers containing higher DMAPS content, whereas the final shape recovery decreases with an increase of DMAPS content. Finally, it is proposed that not only good moisture absorption units are required but also physical crosslinks should be improved for moisture‐sensitive shape memory polymers. Copyright © 2017 John Wiley & Sons, Ltd.     

Conformational search for zwitterionic leucine and hydrated conformers of both the canonical and zwitterionic leucine using the DFT-CPCM model

The stable conformations for zwitterionic leucine have been searched for in solution as well as in gas phase. A total of 54 trial structures were generated by considering possible combinations of single bond rotamers. It is observed that zwitterions are not stable in gas phase. In order to investigate the zwitterions of leucine in solution, the calculations for all trial structures of zwitterions were performed initially at the PM3 level and 14 the lowest energy structures were reoptimized at the B3LYP/6-311G(d) level using the CPCM model. Seven of these conformers of zwitterionic leucine were found to be stable in solution. The five most stable conformers were then reoptimized at the B3LYP/6-311++G(d, p) level. The energy ordering of the canonical leucine(neutral) conformers were also considered on the basis of single point energy calculations at the B3LYP/6-311++G(d, p) level using the CPCM model. The chemical hardness, chemical potential, vertical ionization energy and vertical electron affinity were calculated for a few of the most stable canonical leucine and its zwitterions in solution. The effects of explicit addition of water molecules (microsolvation) on the structure and the energy of both canonical and zwitterionic conformers of leucine were investigated. It is noted that in gas phase, the singly and doubly hydrated canonical (neutral) forms are more stable than their zwitterionic counterparts. The solvated zwitterions and canonical structures of leucine were further investigated using the discrete/SCRF model with zero, one and two water molecules. In solution, the continuum solvent model shows that the bare zwitterionic form is more stable than the bare canonical form by 1.6 kcal/mol. This energy separation is increased to 3.8 and 4.8 kcal/mol with inclusion of one and two water molecules, respectively. The optimized structural parameters for the most stable zwitterionic leucine with zero, one and two water molecules in solution were compared with those reported for l-leucine crystal, which shows a close agreement between the optimized geometrical parameters of the zwitterionic leucine with two water molecules in solution with the experimental geometrical parameters for l-leucine crystal. It is also observed that when the structures of zwitterions with one and two explicit water molecules are optimized in solution, the geometrical parameters and their relative energies are found to be appreciably modified. We have also calculated the vibrational spectra of the most stable solvated zwitterionic leucine as well as for the most stable structure of zwitterionic leucine with one and two water molecules in solution.     

Fabrication of functional nano-objects via self-assembly of nanostructured hybrid materials

A simple route to fabricate functional nano-objects via self-assembly of block copolymer-based hybrid materials is described. In water–toluene mixtures, spheres, rod-like morphologies, and ring-like morphologies as well as vesicles of metal loaded block copolymers micelles are fabricated. The concept is generic to realize different functionalities by incorporating various inorganic components (Au, Ag, Pt, Co…) into the block copolymer matrix. A mechanism describing the formation of micellar aggregates with different morphologies is presented based on a simple force balance approach. Moreover, the composition of the solvent mixture is modified to gain control over the morphology of micellar aggregates. It was found that swelling of the micelle core with a selective cosolvent is the driving force to induce morphology transitions from spherical to rod- and ring-like structures as well as vesicles. These nano-objects can be further used as building blocks to construct well-defined structures via self-assembly in spin coated thin films. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1642–1650, 2010     

RAFT polymerization of tertiary sulfonium zwitterionic monomer in aqueous media for synthesis of protein stabilizing double hydrophilic block copolymers

The reversible addition-fragmentation chain-transfer (RAFT) polymerization of a tertiary sulfonium-containing zwitterionic monomer (N-acryloyl-L-methionine methyl sulfonium salt: A-Met[S⁺]-OH) was performed in aqueous media in the presence of a water-soluble chain-transfer agent (CTA). Several parameters, such as the radical initiator, nature of the salt used as an additive, polymerization temperature, and solvent (water, buffer solution, and mixed solvents), were studied. The polymerization of A-Met(S⁺)-OH in acetate buffer using a trithiocarbonate-type CTA having two carboxylic acid moieties proceeded in a controlled fashion at 45°C, as confirmed by the low polydispersity of the products (M _w/M _n < 1.1) and pre-determined molecular weights. Poly(ethylene glycol)-based macro-CTA was also employed for the polymerization of A-Met(S⁺)-OH in mixed solvents (H₂O/EtOH and H₂O/DMF = 70/30 vol%) to afford novel nonionic-zwitterionic double hydrophilic block copolymers. The chain extension of the hydrophilic poly(N,N-dimethylacrylamide) macro-CTA with A-Met(S⁺)-OH was well controlled in pure water under the appropriate conditions, resulting in the formation of block copolymers with “as-designed” chain structures and relatively low dispersities (M _w/M _n < 1.3). The resulting sulfonium-containing double hydrophilic block copolymers having optimal nonionic/zwitterionic balance were efficient protein-stabilizing agents.     

Multi-step sol-gel process and its effect on the morphology of polyethylene oxide (PEO)/SiO2 anion-exchange hybrid materials

Polyethylene oxide (PEO)/SiO₂ anion-exchange hybrid materials were prepared through the sol-gel process of alkoxysilane functionalized PEO-1000 (PEO-[Si(OCH₃)₃]₂) and N-[3-(trimethoxysilyl)propyl] ethylene diamine (A-1120). The influence of the multi-step sol-gel processing procedure, i.e. the pre-hydrolysis of either of the two precursors on the homogeneity of the hybrid materials was investigated. Results showed that the sol-gel reaction of A-1120 and PEO-[Si(OCH₃)₃]₂ from the same time would result in hybrid materials with the highest homogeneity, and pre-hydrolysis of A-1120 or PEO-[Si(OCH₃)₃]₂ could only decrease the materials’ compatibility.     

Novel approaches for the preparation of magnetic nanogels via covalent bonding

Here, novel methods to encapsulate magnetic nanoparticles (MNPs) into dual‐stimuli‐responsive nanogels via covalent bonding are reported. With the aim of strengthening the attachment of MNPs with the nanogels, primary amine‐ and epoxide‐functionalized stimuli‐sensitive poly(2‐(diethylamino)ethyl methacrylate) (PDEAEMA)‐based nanogels were firstly synthesized. Then, MNPs were incorporated into the nanogels by using different methods, obtaining different families of magnetic nanogels (MNGs). Those MNGs, showing pH‐sensitivity and high superparamagnetic response, could be considered to be widely useful as theranostic agents in biomedical applications. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3573–3586     

Novel anion-exchange organic–inorganic hybrid membranes: Preparation and characterizations for potential use in fuel cells

A new series of supported anion-exchange organic–inorganic hybrid membranes were prepared by quaternizing the copolymer of vinylbenzyl chloride (VBC) and γ-methacryloxypropyl trimethoxy silane (γ-MPS) and then applying a sol–gel reaction to the copolymer and monophenyltriethoxysilane (EPh). The membranes were characterized for potential use in fuel cells. The results show that the physicochemical properties, including ion-exchange property, hydrophilicity, and thermal/chemical stability, can be easily controlled by adjusting the quaternization extent of the copolymer and the dosage of EPh. The hybrid membranes have relatively strong alkali resistance, high temperature tolerance (thermal degradation temperature in air, Td, in the range of 250–300 °C), high tensile strength (TS) and elongation at break (E_b). The hydroxyl ion conductivity is in the range of 2.27–4.33 × 10⁻⁴ S/cm.     

On the investigation of the preparation of inorganic ionic clusters by laser desorption ionization

CeO(H₂O) _n ⁺ cluster ions, withn as large as 20, are generated by laser desorption ionization of a frozen aqueous solution of CeCl₃,7H₂O. A simple dynamic model developed previously can qualitatively account for experimentally observed threshold behavior, and the time- and fluence-dependence of ion signals.Dedicated to Professor Jiaxi Lu on the occasion of his 80th birthday.     

Preparation and characterization of novel negatively charged hybrid membranes

Charged hybrid membranes with anionic‐ or cationic‐exchange groups have attracted increasing interest due to their higher thermal stabilities and structural flexibilities which are considered suitable for use in some harsh conditions, such as higher temperature and strongly oxidizing circumstances, for industrial applications. To develop new routes to synthesize the negatively charged hybrid membranes, a series of hybrid membranes were prepared via free radical polymerization of glycidylmethacrylate (GMA) and γ‐methacryloxypropyl trimethoxy silane (MPTMS) monomers, and ring‐opening of epoxide to create negatively charged ? SO₃H groups in the polymer chains. The fundamental properties of these prepared membranes were characterized through TGA, ion‐change capacity (IEC), and MALDI–TOF mass spectra. TGA showed that the thermal degradation temperature of these membranes could reach up to 300°C and the temperature of the first endothermic peak decreased with an increase in the content of ? SO₃H groups. IEC measurements showed that their IECs were within the range of 0.22–0.35 mmol g^?1. MALDI–TOF spectrometry indicated that the incorporation of GMA into the hybrid matrix could improve the structural stability of the membranes. These findings demonstrated that the ion‐exchange properties and structural stability of negatively charged hybrid membranes can be conveniently controlled by adjusting the GMA moiety in the hybrid matrix. Copyright © 2009 John Wiley & Sons, Ltd.     

Column comparison and method development for the analysis of short‐chain carboxylic acids by zwitterionic hydrophilic interaction liquid chromatography with UV detection

Short‐chain carboxylic acids are relevant in pharmaceutical, food quality control, and biomedical analysis. In this study, 11 acids commonly found in drugs and in food products were selected. Wine was chosen as matrix for testing the method. The test compounds were used for comparing the selectivity of four 150 × 2.1 mm zwitterionic hydrophilic interaction LC (HILIC) columns (ZIC‐HILIC 5 μm, 200 Å, and 3.5 μm, 100 Å, ZIC‐pHILIC 5 μm, ZIC‐cHILIC 3 μm, 100 Å) while varying the conditions to optimize for low UV wavelength detection and achieve high sensitivity. Retention using potassium phosphate and ammonium carbonate as mobile‐phase components at pH 6.0, 7.5, and 8.5–8.9 was studied considering recent hypotheses on HILIC mechanism‐related with the Hofmeister series effect and ion hydration. An isocratic method with UV detection at 200 nm and mobile phase consisting of 75% acetonitrile and 10 mM potassium phosphate at pH 6.0 applied to a ZIC‐cHILIC column was found provisionally optimal and partially validated for the 11 analytes. Satisfactory results (R² from 0.9940 to >0.9999), and recoveries from 93–106% for all analytes evidenced the method as suitable for wine analysis. To the best of our knowledge, no previous study has reported on the direct ZIC‐HILIC separation and UV detection of the acids considered here in wine.     

Functionalized block copolymers for preparation of reactive self‐assembled surface patterns

Two phase separating block copolymers equipped with functional groups (acid and alkyne) were synthesized via reversible addition‐fragmentation chain transfer (RAFT) polymerization. Thin films of these materials were prepared and examined with regard to surface morphology, surface composition, and film stability. Self‐assembled structures with domain sizes of about 40 nm were detected through atomik force microscopy (AFM) analysis while X‐ray photoelectron spectroscopy measurements revealed a balanced surface exposure of the two segregated phases. Thus, reactive groups being present in both phases are specifically provided within nanoscopic surface areas. The films showed good stability on exposure to various solvents but the self‐organized surface patterns were only resistant toward ethanol. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011