Hydrophilic Crosslinking Research Articles

Synthesis of tri-, penta-, and heptasaccharides, functionalized with orthogonally N-protected amino residues at the reducing and non-reducing ends

The synthesis of four bifunctionalized orthogonally N-protected oligosaccharides derived from lactose and mannose, intended as cross-linking derivatives, is described. The amino sugar at the non-re ...

Influence of the Hydrophile-Lipophile Property of Cross-Linker on the Properties of Acrylate Latex and its Film

A series of acrylate latexes for pigment printing binder were prepared by semi-continuous pre-emulsifying emulsion polymerization, using lipophilic glycidyl meth-acrylate (GMA), ethylene glycol dimethyl acrylate (EGDMA) and hydrophilic HA (containing hydroxyl, acylamino), N-methylol acrylamide (NMA) as cross-linking monomer. The influences of cross-linker type on the particle size, viscosity and film-forming rate of latex, cross-linking degree and tensile properties of latex film were studied. It was found that the latex particle size, viscosity and film-forming rate were closely related with the hydrophile-lipophile property of cross linkers. The acrylate latex synthesized with hydrophilic cross-linkers always exhibits the characteristics of larger particle size, lower film-forming rate, higher viscosity and pseudoplastic fluid. The cross-linking degree and tensile properties of latex film generally depend on the crosslinking groups of cross-linkers and their reactivity.

PH-responsive microgels containing hydrophilic crosslinking co-monomers: shell-exploding microgels through design

pH-responsive microgels are crosslinked polymer colloids that swell when the pH approaches the pK a of the particles. They have potential application for injectable gels for tissue repair and drug delivery systems. This study focuses on the pH-triggered gelation behaviour of a series of poly (EA/MAA/X) microgels. EA and MAA are ethylacrylate and methacrylic acid. Here, we investigate the effect of crosslinking monomer type (X) on microgel properties. The crosslinking monomers used were poly (ethyleneglycol) dimethacrylate (PEGD), ethyleneglycol dimethacrylate (EGD) and butanediol diacrylate (BDD). The microgel containing PEGD (m-PEGD) is a new system. The microgel containing BDD (m-BDD) was used as a control system. The concentrated microgel dispersions formed physical gels when the pH was increased to 5.3–6.7, and the polymer volume fractions (ϕ p ) were above about 0.05. Evidence from photon correlation spectroscopy (PCS) and dynamic rheology was presented for abrupt pH-triggered increases, and then decreases of the hydrodynamic diameters for m-PEGD and the microgel prepared using EGD (m-EGD). This appears to be tuneable through crosslinker structure. An unexpected gelation behaviour, which may involve a new gel state for microgels, was found for m-PEGD dispersions. Uniquely, those dispersions formed gels at pH values less than the microgel's pK a . This behaviour was linked to an outer-shell electrostatic repulsive interaction. The data point to a phenomenon, whereby the m-PEGD shells appear to explode at pH values above 7.0. The control microgel prepared, using BDD (m-BDD), did not show any evidence of shell fragmentation at any pH. That microgel has potential as a model pH-responsive microgel system in that the properties measured by PCS and rheology agreed well. To probe that system in more detail, the rheological data for m-BDD was analysed using scaling theory. The variation of the storage modulus (G') with ϕ p gave a scaling exponent of 2.0.

Tailoring thermoresponsive microbeads in supercritical carbon dioxide for biomedical applications

Abstract The preparation of smart polymeric particles in supercritical carbon dioxide (scCO 2 ) presents many advantages for biomedical applications over conventional processes due to the easy elimination of trace contaminants rendering highly pure particles. Herein we report the successful optimization of poly( N -isopropylacrylamide) (PNIPAAm) synthesis strategy to obtain cell-sized hydrogel microbeads with defined and systematically varied mechanical properties. The effect of using different hydrophilic cross-linkers such as N , N -methylenebisacrylamide (MBAm), di(ethylene) glycol dimethacrylate (DEGDMA) and glycerol dimethacrylate (GDMA), on beads morphological, physico-chemical and mechanical properties was investigated. In agreement with a larger water uptake ability beads cross-linked with DEGDMA are more compliant than those containing MBAm or GDMA, having lower stiffness as accessed through oscillatory measurements on a rotational rheometer. Cytotoxicity assays showed that the obtained cross-linked PNIPAAm microbeads do not present any toxic effect on fibroblast cell cultures. Microbeads biocompatibility and adequate mechanical compliance enable their potential application on biomedical settings.

Modification of Polysiloxane Networks for Biocompatibility

The hydrophobic characteristics of polysiloxane networks somewhat limit their wide applications in biomedical fields in spite of their many promising properties. In this paper, several surface and bulk modifications to bimodal poly(dimethylsiloxane) (PDMS) networks are described to improve surface hydrophilicity as well as biocompatibility. Surface modification methods employed were ultraviolet/ozone-induced grafting hydrophilic monomer polymerization, plasma induced-surface grafting polymerization, and surface direct chemical bonding. Bulk modifications were carried out by using hydrophilic block copolymers and cross-linkers having hydrophilic dangling chains, which also conferred high surface hydrophilicity. The experimental results showed that the surface hydrophilicity was greatly improved, i.e., there were decreases from a static water contact angle of about 105° in pristine PDMS to about 20° in poly(ethylene oxide)/PDMS amphiphilic conetworks having linear dangling chains consisting of 6–9 units. The hydrophilic nature lasted at least 30 days, especially in the case of the application of the hydrophilic cross-linker in the networks. Some other properties including mechanical behavior, equilibrium water swelling content, surface characteristics, and morphology were also investigated.

Design and development of temperature sensitive porous poly(NIPAAm‐AMPS) hydrogels for drug release of doxorubicin‐a cancer chemotherapy drug

AbstractTemperature sensitive polymer network porous hydrogels were developed with N‐Isopropylacrylamide (NIPAAm) and AMPS (2‐acrylamido‐2‐methyl‐1‐propanesulfonicacid), as well as with sucrose as porogen by crosslinking with hydrophilic crosslinker N,N1‐methylenebisacrylamide (MBA). The temperature responsive behaviour, the swelling/deswelling kinetics of the hydrogels were investigated. The structural and morphological characterizations of the developed hydrogels were obtained from FTIR spectroscopy and scanning electron microscopy (SEM). The increment in the lower critical solution temperature (LCST) of NIPAAm hydrogels can be done with the help of AMPS and it is confirmed with differential scanning calorimetry (DSC) as well as temperature dependent swelling curves. The model cancer chemotherapy drug Doxorubicin (Dox) was loaded into theses hydrogels and the release studies as well as the released profiles of the drug showed that more than 8–54% of the loaded drug was released in the first half‐an‐hour at a buffer solution of 7.4 and the rest of the drug was released slowly. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Synthesis of hydrophilic boronate affinity monolithic capillary for specific capture of glycoproteins by capillary liquid chromatography

Boronate affinity chromatography is an important tool for specific isolation of cis-diol-containing compounds such as glycoproteins, RNA and carbohydrates. Boronate functionalized monolithic capillaries have been recently developed for specific capture of cis-diol-containing small biomolecules, but the apparent hydrophobicity of the columns prevents them from specific capture of glycoproteins. In this paper, a hydrophilic boronate affinity monolithic capillary was prepared by in situ free radical polymerization, using 4-vinylphenylboronic acid (VPBA) and N, N'-methylenebisacrylamide (MBAA) as functional monomer and cross-linker, respectively. The prepared poly(VPBA-co-MBAA) monolithic capillary exhibited uniform open channel network and high density of accessible boronic acid. Due to the utilization of hydrophilic cross-linker, the prepared column was hydrophilic, allowing for specific capture of glycoproteins.

Water-compatible imprinted polymers for selective depletion of riboflavine from beverages

Artificial riboflavin receptors adapted to aqueous environments were studied for their ability to selectively extract riboflavine (Rf) from three types of beverages i.e. milk, beer and a multivitamin mixture. The basic receptor was first prepared by molecular imprinting in nonaqueous medium using a hydrogen-bond donor–acceptor-donor functional monomer (2,6-bis(acrylamido)pyridine), complementary to the imide motif of the template, riboflavin tetra-acetate as template and pentaerythritol triacrylate (PETA) as a hydrophilic cross-linking monomer. The polymer was then packed in columns and used for extraction of riboflavine from beverages. Riboflavine (Rf) was selectively removed from milk and an artificial vitamin mixture but the nonspecific binding was still significant, as judged from the binding of Rf to a control nonimprinted polymer. In order to suppress this nonspecific binding, attempts to hydrolytically hydrophilize the polymer matrix were performed. The preferred approach consisted in a controlled base hydrolysis of pendent unreacted acrylate groups, using hydroxides with differently sized counterions as reagents. This resulted in a decreased binding of Rf to both polymers, but to an equal extent implying a preferential suppression of the nonspecific contribution to the binding. The hydrophilized polymers, when subjected to beer, showed larger imprinting factors at lower phase ratios compared to the nontreated polymers and a maximum removal of 86% compared to 47% for the nonimprinted control polymer.

Adhesive Bonding to Dentin Improved by Polymerizable Cyclodextrin Derivatives.

The objective of this work was to determine bonding characteristics of a hydrophilic monomer formulation containing polymerizable cyclodextrin derivatives. The hypothesis was that a formulation containing hydrophilic cross-linking diluent comonomers and cyclodextrins with functional groups attached by hydrolytically stable ether linkages could form strong adhesive bonds to dentin. The previously synthesized polymerizable cyclodextrin derivatives were formulated with sorbitol dimethacrylate, methacrylic acid and phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide photoinitiator. The same formulation without the polymerizable cyclodextrin derivatives isolated the effects of the polymerizable cyclodextrin derivatives. A commercial self-etching bonding system was tested as a comparative control. Ground mid-coronal dentin was etched with 37 % phosphoric acid (H3PO4) for 15 s and rinsed with distilled water for 10 s. Formulations were applied to the moist dentin and light-cured 10 s. A packable composite was then applied through irises and light-cured 60 s. Teeth were stored in water for 24 h before bonds were tested in a shearing orientation. One-way ANOVA was performed on the data. The average values of shear bond strengths were defined as loads at fracture divided by the 4 mm diameter iris areas. The average value of shear bond strength for the formulation containing the polymerizable cyclodextrin derivatives was higher (p < 0.05), where p is a fraction of the probability distribution) than that of the same monomeric formulation except that the polymerizable cyclodextrin derivatives were not included. This was supporting evidence that the polymerizable cyclodextrin derivatives contributed to improved bonding. The average value of shear bond strength for the formulation containing the polymerizable cyclodextrin derivatives was also higher (p < 0.05) than that of the commercial self-etching bonding system. These preliminary results are in accordance with the hypothesis that formulations containing polymerizable cyclodextrin derivatives can form strong adhesive bonds to hydrated dentin surfaces. Further improvements in bonding to hydrated biological tissues by use of advanced formulations are anticipated.

Effect of Crosslinker Type and Embedded Magnetite on the Uptake Behavior of Amine Containing Glycidyl Methacrylate Resins towards Iron(III)

Copolymerization of glycidyl methacrylate (GMA) in the presence of divinylbenzene (DVB) or N,N′‐methylene bis‐acrylamide (MBA) as hydrophobic or hydrophilic crosslinker was carried out. The obtained resins were immobilized with tetraethylenepentamine as active moieties. The (MBA) containing resin showed higher uptake capacity (9.0 mmol/g) towards Fe(III) compared to (DVB) containing one (8.1 mmol/g). Moreover, magnetization of (GMA/MBA) resin by embedded Fe3O4 dramatically improved its uptake towards Fe(III) to reach 13.0 mmol/g at 28°C. Kinetic studies indicated that the adsorption of Fe(III) by the investigated resins follows the pseudo second order kinetics. The higher efficiency of the magnetic resin towards uptake of Fe(III) was also confirmed through column studies. Regeneration of the resins was achieved using acidified thiourea with HNO3. The durability of the resins was checked up to 5 cycles with no appreciable change in uptake capacity or durability.

Development and characterisation of novel cross-linked bio-elastomeric materials

Recombinantly-engineered elastin-like polypeptides (ELPs) possess many of the favourable attributes of the native elastin protein, making them an attractive option for designing biomaterials for tissue-engineering applications. The focus of this study was to synthesize and characterise the bulk material properties of two ELP sequences, ELP2 and ELP4, cross-linked with lysine diisocyanate (LDI). The two distinct ELPs consist of repeating hydrophobic and hydrophilic cross-linking domains in a block co-polymer structure, however, differ by the number of respective domains. Depending on the conditions sets for the cross-linking reactions, two different ELP-based materials were synthesized: a gel-like relatively non-porous material and a porous foam-like material, from both ELP sequences. The physical material properties were characterised by scanning electron microscopy, compression testing, differential calorimetry analysis and swelling analysis. The bulk material properties were found to vary depending on the ELP sequence investigated. ELP gels were also found to have a more dense solidified morphology, lower compressive moduli, higher melting temperature and greater swelling capacity than the porous ELP foams. These novel cross-linked bio-elastomeric materials show promising properties for soft tissue replacement, particularly in load-bearing applications.

Synthesis of magnetic chelating resins functionalized with tetraethylenepentamine for adsorption of molybdate anions from aqueous solutions

Magnetic resins were synthesized through polymerization of glycidyl methacrylate (GMA) in the presence of divinylbenzene (DVB) or N,N'-methylenebisacrylamide (MBA) as hydrophobic or hydrophilic crosslinker, respectively and in presence of suspended magnetite particles. The resins containing (DVB or MBA) as crosslinker were immobilized with tetraethylenepentamine (TEP) to give the amino resins, GMA/DVB/TEP (R1-en) and GMA/MBA/TEP (R2-en), respectively. The uptake behavior of the two resins was studied towards molybdate anions and uptake capacities of 4.24 and 6.18 mmol/g [as (Mo(VI)] were obtained using (R1-en) and (R2-en). Kinetic studies showed that the adsorption followed the pseudo-second-order model pointing the influence of the textural properties of the resin on the rate of adsorption. Thermodynamic data indicated an endothermic adsorption process. The uptake of Mo(VI) and regeneration of the resins were also studied using the column method. Regeneration efficiency up to 90-96% was reached using ammonia buffer.

Hydroxyl functionalized thermosensitive microgels with quadratic crosslinking density distribution

N-isopropylacrylamide (NIPA) based uniform thermosensitive microgels were synthesized by dispersion polymerization by using relatively hydrophilic crosslinking agents with hydroxyl functionality. Glycerol dimethacrylate (GDMA), pentaerythritol triacrylate (PETA) and pentaerythritol propoxylate triacrylate (PEPTA) were used as crosslinking agents with different hydrophilicities. A protocol was first proposed to determine the crosslinking density distribution in the thermosensitive microgel particles by confocal laser scanning microscopy (CLSM). The microgels were fluorescently labeled by using hydroxyl group of the crosslinking agent. The CLSM observations performed with the microgels synthesized by three different crosslinking agents showed that the crosslinking density exhibited a quadratic decrease with the increasing radial distance in the spherical microgel particles. This structure led to the formation of more loose gel structure on the particle surface with respect to the center. Then the use of hydrophilic crosslinking agents in the dispersion polymerization of NIPA made possible the synthesis of thermosensitive microgels carrying long, flexible and chemically derivatizable (i.e., hydroxyl functionalized) fringes on the surface by a single-stage dispersion polymerization. The microgels with all crosslinking agents exhibited volume phase transition with the increasing temperature. The microgel obtained by the most hydrophilic crosslinking agent, GDMA exhibited higher hydrodynamic diameters in the fully swollen form at low temperatures than those obtained by PETA and PEPTA. Higher hydrodynamic size decrease from fully swollen form to the fully shrunken form was also observed with the same microgel.

Effects of chemical modifications on the swelling behaviors of poly (4-vinyl phenol) gel

Poly (4-vinyl phenol) (P4VPh) gels were prepared by crosslinking with a hydrophilic crosslinker [ethyleneglycoldiglycidylether (EGDGE)] and a hydrophobic one [diglycidyl 1,2-cyclohexane dicarboxylate (DGCHDC)], and the former gel was further modified by CH3I or C2H5I to partially convert the hydrogen of phenol OH to the corresponding alkyl groups. Swelling behaviors of P4VPh gels, thus modified, were investigated to see how the hydrophobic groups introduced to the crosslinker and the polymer substrate affect the super salt resistivity to inorganic ions and the high water content (>90%) that have been observed for the original P4VPh gel. Water content and salt resistivity were unexpectedly preserved even for the modified gels. Effects of the chemical modifications on the gel swelling were only observed in the presence of hydrophobic solutes, i.e., tetrabutyl ammonium chloride and ionic surfactants. All these results strongly suggest that hydration around the polymer substrate in the gel phase is specifically stabilized, probably because of the coexistence of the hydrophobic hydration and the π-hydrogen-bonding hydration around the phenol ring.

Synthesis and Swelling Behavior of Acrylamide-Potassium Methacrylate Superabsorbent Copolymers

ABSTRACT A series of acrylamide-potassium methacrylate superabsorbent copolymers were synthesized by simultaneous free radical aqueous polymerization using acrylamide (AAm), potassium methacrylate (KMA), and ammonium persulfate (APS)/ N,N,N′,N′-tetramethylethylenediamine (TMEDA) as initiating system in the presence of a crosslinker. The effects of variables such as concentration of hydrophilic monomer (KMA), crosslinker, initiator and activator, and polymerization temperature on swelling capacity have been investigated in detail. In these polymerizations, two different crosslinking agents, namely 1,4-butanediol diacrylate (BDDA) and ethylene glycol dimethacrylate (EGDMA), were employed to study the effect of crosslinker on swelling properties. The swelling kinetic parameters as well as type of water diffusion into the polymer matrix were evaluated at different temperatures for two series of superabsorbent copolymers. The swelling experiments revealed that EGDMA crosslinked superabsorbents have shown higher swelling capacity for all the compositions of AAm/KMA ratio than BDDA crosslinked analogues. Further, the salt sensitivity and de-swelling capacity of the superabsorbent polymers were studied. The pH effect on the swelling ratio of crosslinked copolymers was also investigated.

Synthesis of hydrophilic cross-linker having phosphorylcholine-like linkage for improvement of hydrogel properties

Abstract As a novel cross-linking reagent, dimethacrylate having a phosphorylcholine-like linkage, called 2-(methacryloyloxy)ethyl-[ N -(2-methacryloyloxy)ethyl]phosphorylcholine (MMPC), was synthesized by condensation between methacrylate having a cyclic phosphate and that with a tertiary amine group. The MMPC was copolymerized with 2-methacyloyloxyethyl phosphorylcholine (MPC) or 2-hydroxyethyl methacrylate (HEMA) to produce the polymer hydrogels. The polymerization initiated by a redox system in aqueous medium proceeded well and the hydrogel was formed. The swelling of the poly(MPC) hydrogel was regulated by the MMPC composition. For the poly(HEMA) gel cross-linked with MMPC, the swelling degree was almost the same in the MMPC composition range of 1.0–10 mol%. However, the transparency of the poly(HEMA) gel increased with an increase in the MMPC. The MMPC is a useful cross-linker to make hydrogels and control the swelling and property of the hydrogel.

An Examination of the Gelation of Methacrylate Type Crosslinking Agents for the Preparation of Polymer Monolith with 3D Ordered Network Structures

Abstract The gelation of dimethacrylate type crosslinking agents was studied from the perspective of formation of ordered three dimensional (3D) network structures. Dynamic light scattering (DLS) data showed that the gelation of hydrophilic crosslinking agents having OH groups such as glycerol dimethacrylate (GDMA) was enhanced through hydrogen bonding in a hydrophobic solvent system such as toluene, which afforded more ordered 3D structures.

Capillary electrochromatography with polymeric continuous beds synthesized via free radical polymerization in aqueous media using derivatized cyclodextrins as solubilizing agents

A novel synthetic route to amphiphilic acrylamide-based monolithic stationary phases for capillary electrochromatography (CEC) employing water-soluble cyclodextrins as solubilizing agents was explored. N,N'-Octamethylenebisacryamide and N,N'-dodecamethylenebisacryamide were synthesized and their solubilization in aqueous solution with derivatized and underivatized cyclodextrins of different cavity size was studied. Amphiphilic stationary phases were synthesized by free radical copolymerization of the bisacrylamide-cyclodextrin host-guest complexes with hydrophilic monomers and an additional hydrophilic cross-linker in aqueous solution. Complex formation in solution and removal of the complexed cyclodextrin from the polymer during synthesis was studied with 1H-NMR and solid state 13C-NMR spectroscopy and cyclodextrin-modified micellar electrokinetic chromatography. The impact of the incorporated alkylene groups in the acrylamide-based macroporous polymer on retention was studied with neutral solutes by CEC in the normal-phase elution mode and in the reversed-phase elution mode. Batch-to-batch reproducibility of the synthesis procedure and day-to-day repeatability of the separations achieved were investigated. With these capillaries, a sufficiently high electroosmotic flow velocity, a high reproducibility and repeatability of separation parameters and high plate numbers (up to 200,000 m(-1) were obtained.

Effects of hydrophilicity of crosslinker on membrane properties of poly( N -hydroxyethyl-L-glutamine) hydrogels

Poly(N-hydroxyethyl-L-glutamine) (PHEG) hydrogels were prepared by aminolysis of poly( γ-benzyl L-glutamate) with 2-aminoethanol and hydrophobic or hydrophilic crosslinkers, and the effect of the hydrophobicity of the crosslinkers was evaluated. The swelling properties, tensile properties and enzymatic degradation behavior were studied in phosphate buffered saline (PBS). The swelling ratio and degradation rate of these hydrogels were highly dependent on the hydrophobicity of the crosslinkers, while tensile properties were dependent on the swelling ratio, but not on the hydrophobicity of the crosskinkers.

Poly(1-vinyl-2-pyrrolidinone) hydrogels as vitreous substitutes: a rheological study

In order to develop an artificial vitreous, a large series of hydrogels have been previously produced by polymerization of 1-vinyl-2-pyrrolidinone, with or without crosslinking. Based on the assumption that a functional vitreous substitute should possess viscoelastic properties after its delivery, a number of selected gels were characterized rheologically by both oscillatory shear stress analysis and shear creep analysis, using a controlled stress rheometer in the cone/plate configuration. The experiments demonstrated a dramatic effect of injecting the gels through small-gauge needles, as many lost their viscoelasticity to become free-flowing fluids, probably because of the cleavage of chains and crosslinks. It was also found that the increase of comonomer content (2-hydroxyethyl methacrylate) and of crosslinking level generally had a strengthening effect. However, the effects of hydrophilic crosslinking agents (diallyl ether and divinyl glycol) were irregular. Eventually, only four hydrogels in this series showed viscoelastic characteristics after injection through a 30-gauge (0·13mm diameter) needle, maintaining behaviour typical of crosslinked networks and warranting further assessment as potential vitreous substitutes. © 1998 SCI.