Hydrophilic Monomers 2-hydroxyethyl Methacrylate Research Articles

Effect of Collagen-Reactive Functional Monomer on Etch-and-Rinse Adhesives

In this study, we evaluated a novel functional monomer (4-formylphenyl acrylate [FA]) that can specifically and covalently bind to the dentin collagen matrix as a potential alternative hydrophobic diluent-like monomer for improving the durability of dentin bonding. Experimental adhesives with different FA contents (0%, 10%, 20%, and 30%) were evaluated as partial substituents for the hydrophilic monomer 2-hydroxyethyl methacrylate, with the commercial adhesive One-Step (Bisco, Inc.) employed as the positive control. Their degree of conversion, viscosity, hydrophobicity, mechanical properties, and water absorption/solubility were measured as the comprehensive characterization. In situ zymographic assays were performed to determine the extent to which FA inhibits the endogenous hydrolytic activity of dentin. Finally, the bonding performances of the novel adhesives were evaluated with microtensile strength tests and scanning electron microscopy. The results showed that the incorporation of FA significantly improved the mobility of experimental adhesives attributable to the dilution property of FA. In contrast to the possible compromised rate of polymerization by hydroxyethyl methacrylate, FA exhibited typical characteristics of favorable copolymerization with polymerizable monomers in adhesives and improved the degree of conversion of experimental adhesives. The rigidity and hydrophobic properties of the phenyl framework of the FA molecule conferred superior mechanical properties and hydrolysis resistance to the novel experimental adhesives. An inhibitory effect on gelatinolytic activities within the hybrid layer was also observed in the in situ zymographic assays, even at a low FA concentration (10%). In conjunction with the significantly improved infiltration found via scanning electron microscopy, the experimental adhesives containing FA possessed significantly better-maintained microtensile strength, even after aging. Thus, the incorporation of this novel monomer endowed the experimental adhesives with multiple enhanced functionalities. These remarkable advantages highlight the suitability of the monomer for further applications in clinical practice.

Dual-crosslinked bioprosthetic heart valves prepared by glutaraldehyde crosslinked pericardium and poly-2-hydroxyethyl methacrylate exhibited improved antithrombogenicity and anticalcification properties

Bioprosthetic heart valves (BHVs) have been widely used due to the revolutionary transcatheter aortic valve replacement (TAVR) techniques but suffer from a limited lifespan. Previous modification methods of BHVs mainly rely on glutaraldehyde precrosslinking and subsequent modification. In this study, we have engineered a Poly-2-Hydroxyethyl methacrylate (pHEMA) coated BHV based on co-crosslinking and co-polymerization strategies. Our BHV overcomes previous limitations of glutaraldehyde prefixation by introducing free molecules before crosslinking to achieve the crosslinking and allyl moiety immobilization simultaneously. Decellularized porcine pericardium and 2-Amino-4-pentenoic acid (APA) are firstly co-crosslinked by glutaraldehyde to obtain alkenylated porcine pericardium (APA-PP), then APA-PP is copolymerized with hydrophilic monomer 2-Hydroxyethyl methacrylate (HEMA) to prepare pHEMA grafted porcine pericardium (HEMA-PP). Compared with traditional glutaraldehyde crosslinked pericardium (GA), HEMA-PP exhibits decreased cytotoxicity and significantly increased endothelialial cells proliferation (7-folds higher than GA after 3-day incubation). In vitro and ex vivo hemocompatibility studies demonstrate the superiority of HEMA-PP in anti-thrombogenicity, where the platelet adhesion decreased by levels of approximately 89% compared to GA. Moreover, HEMA-PP maintains structurally stable with a low level of calcification in the subcutaneous model. The hydrodynamic performance and durability are proven to meet the requirements of ISO 5840-3. Altogether, HEMA-PP may have the potential for future clinical application. Statement of significanceCurrently, bioprosthetic heart valves (BHVs) have drawbacks including cytotoxicity, calcification and thrombosis, which would accelerate structural valvular degeneration and limit the service life of BHVs. We developed a new modification strategy that could simultaneously improve the biocompatibility, anti-calcification and anti-thrombotic properties of BHVs. Moreover, the appropriate durability and hydrodynamic property demonstrated the potential of our strategy for clinical application. This work will potentially prolong the service life of BHVs and provide new insight for the modification of BHVs.

Grafting of 2-hydroxyethyl methacrylate onto polyacrylonitrile using supercritical carbon dioxide

Supercritical carbon dioxide (SCCO2) was used in this study for the surface modification of polyacrylonitrile (PAN) membrane. A two-step process was used to graft the hydrophilic monomer, 2-hydroxyethyl methacrylate (HEMA), by the free radical polymerization onto PAN. The first step was the soaking of the initiator, 2,2′-azobisisobutyronitrile (AIBN), into the SCCO2-swollen PAN. The second step involved the grafting reaction of HEMA through the pre-soaked AIBN on the surface of PAN in SCCO2. A grafting percentage up to 30 wt% was obtained under the optimal reaction temperature at 70 °C and pressure at 17.5 MPa. The modified PAN surface was coated with domains of HEMA that improved the hydrophilicity after the reaction process. The static contact angle of the polymer surface changed from the initial value of 55° to 27° after the optimal PAN surface modification process.

Nitric Oxide-Generating Antiplatelet Polyurethane Surfaces with Multiple Additional Biofunctions via Cyclodextrin-Based Host-Guest Interactions.

A nitric oxide-generating polymeric coating was prepared by copolymerization of the hydrophilic monomer 2-hydroxyethyl methacrylate (HEMA) and the comonomer 1-adamantan-1-ylmethyl methacrylate (AdaMA) with subsequent incorporation of selenocystamine. The coating was applied to polyurethane (PU) as a substrate. In the presence of a NO donor, the PU-PHA-Se surface generated nitric oxide (NO). This surface was shown to inhibit platelet adhesion and human umbilical vein smooth muscle cell adhesion and proliferation. The poly(AdaMA) on the modified surface was designed to allow the incorporation of functional units into the PU-PHA-Se surface via host-guest interactions between the adamantane groups and cyclodextrin (CD) derivatives. In this work, two functional CD complexes containing lysine (CD-L) and sulfonate (CD-S) groups were incorporated into the PU-PHA-Se surface. CD-L conferred fibrinolytic activity, whereas CD-S promoted human umbilical vein endothelial cell proliferation. This NO-generating antiplatelet polymeric coating has potential as a platform for modifying surfaces with multiple additional biological functions via host-guest interactions, thus providing an alternative approach for the preparation of biomaterials with multifunctionality.

Adsorption and release of nicotine from imprinted particles synthesised by precipitation polymerisation: Optimising transdermal formulations

Molecularly imprinted polymers (MIPs) are promising materials that can be used as advanced pharmaceutical excipients in the development of formulations for sustained release of drugs. In previous studies, we developed formulations for the transdermal administration of nicotine based on MIPs synthesised by bulk polymerisation that were able to control skin permeation rate of the drug for 24 h following a Higuchi kinetic. In this work, we optimise the synthesis protocol using the precipitation polymerisation technique. MIPs, including the hydrophilic monomer 2-hydroxyethyl methacrylate (HEMA), were selected for their improved adsorption capacity and selectivity in comparison with non-imprinted polymers (NIPs). Adsorption data were better fitted to Langmuir-Freundlich model, indicating heterogeneity of the binding sites. MIPs showed swelling 3–5 times larger than NIPs in aqueous media, while swelling studies in mineral oil (non-polar vehicle) did not indicate differences between these materials. Formulations prepared using mineral oil as vehicle indicated that MIP-based formulations showed a faster release than those based on NIPs, which was related to their increased swelling with the release medium. Skin permeation studies using ear porcine skin indicated that MIP-based formulations with high nicotine loading were able to control the skin permeation flux following zero order kinetic for prolonged times (48 h). The permeation rate from these MIP formulations was lower than from NIP formulations. Thus, these results were associated with limited swelling of MIPs during in vitro skin permeation assays, and the selective desorption of nicotine from MIP particles.

Adherence of Pseudomonas aeruginosa onto surfactant-laden contact lenses

There is an immense research interest to utilise contact lens (CLs) as a popular platform for ocular drug delivery. However, CLs are the major predisposing factors of bacterial keratitis which is commonly caused by adhesion of microbes such as Pseudomonas aeruginosa and Staphylococcus epidermidis. The aim of the current study is to explore the effect of surfactants; Poloxamer 188, Polysorbate 80 and Tetronic® 90R4 (at 0.25% – 3% v/v) on the characteristics of CLs and on the adhesion abilities of Pseudomonas aeruginosa to the lenses’ surfaces. CLs were formulated using a hydrophilic monomer; 2-hydroxyethyl methacrylate (HEMA) together with silicone-based polymer such as Poly dimethyl siloxane (PDMS) or 3,3,3-trifluoropropylsilane (FSA) then lenses were polymerized under UV light. The formulated CLs with surfactants were found to have an increased equilibrium water content (EWC) due to hydrophilic moiety present in surfactants. A relationship was deduced between EWC and surface contact angle of lenses containing surfactants; where an increased EWC was associated with a decrease in contact angle reflecting a more hydrophilic surfaces of CLs. Apart from the 3% Polysorbate 80 (p < .0001) CLs, all other formulations had light transmission values over 80%. Lenses with surfactants were found to have lower bacterial ATP concentration than lenses without surfactants. Poloxamer 188 in FSA lenses reduced bacterial adhesion from 4.22 × 10−4 ± 1.30 × 10−4 pM to 1.03 × 10−4 ± 4.86 × 10−5 pM, a reduction by 75.59% when compared to the control lenses (p = .002). Moreover, 1% Tetronic® 90R4 in PDMS showed a reduction by 57.17% in ATP concentration. Polysorbate 80 in FSA exhibited the least bacterial adhesion with an average bacterial ATP concentration of 3.85 × 10−5 ± 2.61 × 10−5 pM; i.e 90.88% less bacterial ATP than control lenses (p = .001). Bioluminescence studies demonstrated a decrease in Pseudomonas aeruginosa adhesion to CLs containing surfactants without impairing the optical and mechanical characteristics of the lenses.

Influence of polymer composition on the sensitivity towards nitrite and nitric oxide of colorimetric disposable test strips.

The influence of polymer composition on the sensitivity towards nitrite (NO2-) and nitric oxide (NO) of a series of 19 polymeric hydrogel films has been studied. The polymers, based on the hydrophilic monomer 2-hydroxyethylmethacrylate (HEMA), are able to encapsulate the colorimetric indicator 1,2-diaminoanthraquinone (DAQ) and to respond to NO2- and NO by visual changes. In the case of nitrite, the calculated limits of detection (LOD) for two of the polymeric sensors (10μM) are very close to the sensitivity estimated for free DAQ in solution (LOD 5μM), but with the advantage of a solid supported sensor with the format of a disposable test-strip made with affordable starting chemicals. The results are interpreted taking into account the nature and proportions of monomers and cross-linkers used for the synthesis of polymers. Key factors for obtaining sensitive materials are the hydrophilic character of the film along with the utilization of low levels of cross-linker and the use of an acidic monomer, like acrylic acid, as a building block.

A multi-responsive multicomponent hydrogel with micro-phase separation structure: Synthesis and special drug release

In this article, the multicomponent hydrogel was prepared by the copolymerization of the hydrophobic silicon-containing monomer tris(trimethylsiloxy)-3-methacryloxypropyl-sliane (TRIS) with the hydrophilic monomers 2-hydroxyethyl methacrylate (HEMA) and N-vinyl pyrrolidone (NVP). The ethanol extraction experiments as well as the FTIR, DSC results showed that the copolymerization was effective. The silicone hydrogel that had hydrophilic and hydrophobic phases could be loaded with hydrophilic drug (FITC) and hydrophobic drug (Nile Red) simultaneously. The drug release properties of the hydrogel were studied by taking advantage of its innate stimuli-responsiveness to solvent and pH. The release behaviors of hydrophilic and hydrophobic drugs were found to be solvent dependent. And the release behavior of hydrophilic drug was also pH sensitive. With the characteristics above, the silicone hydrogels can be good candidates for specified materials and may have broad applications in responsiveness, drug release, contact lens, etc.

The relationship between oxygen permeability and phase separation morphology of the multicomponent silicone hydrogels.

In this article, the multicomponent copolymers were prepared by the copolymerization of two hydrophobic silicon-containing monomers bis(trimethylsilyloxy) methylsilylpropyl glycerol methacrylate (SiMA) and tris(trimethylsiloxy)-3-methacryloxypropylsilane (TRIS) with three hydrophilic monomers 2-hydroxyethyl methacrylate, N-vinylpyrrolidone, and N,N-dimethyl acrylamide. The copolymers were hydrated to form transparent silicone hydrogels. The oxygen permeability coefficients (Dk) of hydrogels were measured, and their relationships with the equilibrium water contents (EWC) and the types and contents of silicon containing monomers as well as the phase separation structures of silicone hydrogels were analyzed in detail. The results showed that the EWC decreased as the increase of SiMA content. The relationship between Dk and SiMA content, as well as that between Dk and EWC, showed inverted bell curve distributions, which meant two main factors, i.e., silicon-oxygen bond in silicone and water in hydrogel, contributed to oxygen permeation and followed a mutual inhibition competition mechanism. The internal morphologies of the hydrogels were observed by transmission electron microscope, and the results showed that the hydrogels presented two different phase separation structures depending on the types of the silicon-containing monomers. The silicone phase in SiMA containing hydrogel presented to be a granular texture, while the silicone phase in TRIS containing hydrogel formed a fibrous texture which resulted in a higher Dk value. These results could help to design a silicone hydrogel with better properties and wider application.

Postmodification of PS-b-P4VP diblock copolymer membranes by ARGET ATRP.

The surfaces of polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymer membranes were modified in order to obtain polymer brushes by using surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). Isoporous membranes were prepared by the combination of self-assembly of PS-b-P4VP diblock copolymers and the nonsolvent induced phase separation process, also known as "phase inversion". In order to allow further functionalization, the membranes were modified with an ATRP initiator, 2-bromoisobutyryl bromide (BIBB). Therefore, the mussel-inspired poly(dopamine) coating was used to attach BIBB on the membranes surface. In the next step the coated membranes were postmodified by using surface-initiated ARGET ATRP with the hydrophilic monomer 2-hydroxyethyl methacrylate (HEMA). HEMA as a hydrophilic methacrylate was chosen for the modification in order to enhance the membrane characteristics and to obtain a surface with antifouling properties. The surface-initiated ARGET ATRP reaction was carried out using different reaction times and environments. PHEMA could successfully incorporate on the membrane surface as confirmed by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), (1)H nuclear magnetic resonance spectroscopy ((1)H NMR), scanning electron microscopy (SEM), and contact angle measurements. Furthermore, stability tests against heat and solvents were performed, and water flux was measured for the raw and modified membranes. Stability against heat and hydrophilicity could be increased with this type of modification for diblock copolymer membranes.

Surface modification of vulcanized rubber by radiation grafting, part 2: Improvement in performance of wiper rubber

AbstractSurface of natural rubber was modified by radiation‐induced grafting of hydrophilic monomer, 2‐hydroxyethyl methacrylate (HEMA), to improve the properties of surface hardness, dry friction, wiping performance, and wear duration. The ratio of grafted‐HEMA to the rubber near the surface layer of HEMA‐grafted rubber was analyzed by FT‐IR and expressed as composition ratio. The composition ratio was controlled from 0.29 to 0.93 by changing HEMA concentration and dose in graft polymerization. When this composition ratio was higher than 0.8, the surface hardness was higher than 70 and the coefficient of dry friction lower than 0.65. Those values became better than those of commercially available chlorinated‐rubber in terms of wear and friction against glass. The surface hardness in wet state became very close to natural rubber since grafted‐HEMA was softened by contacting with water. As a result, the grafted‐HEMA rubber realized 95% and higher wiping performance of water on glass. Additionally, the wear resistance was eight times higher than chlorinated rubber. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Low-temperature (below Tg) thermal bonding of COC microfluidic devices using UV photografted HEMA-modified substrates: high strength, stable hydrophilic, biocompatible surfaces

Cyclic olefin copolymer (COC) based microfluidic devices offer unique opportunities in developing high quality chips for a variety of applications but critical issues such as the bonding strength, biocompatibility and flow need to be addressed before this can be realized. In this study, we introduce a simple microfluidic device fabricated on COC (Topas) substrates that were modified by ultraviolet (UV) photo-grafting of a hydrophilic monomer 2-hydroxyethyl methacrylate (HEMA). This water soluble acrylic monomer was used to increase the bond strength, surface wettability and hemocompatibility. Thermal bonding of the microfluidic chips was accomplished at temperatures well below the glass transition temperature (Tg) of the COC polymer. Moreover, this process produced COC microchannels with modified surfaces that had stable permanent hydrophilic properties. Therefore, it can be used for Bio-MEMS applications in electrophoretic analysis where stable electro-osmotic flow (EOF) is important. The bond strength and burst pressure of the HEMA modified chips increased significantly to 1.70 MPa and 4.20 MPa for bonding at 10 °C below Tg. The COC surfaces were characterized using contact angle, EOF measurements, and Fourier transform infrared spectroscopy. The hydrophilicities of the substrates improved significantly with increase in degree of poly-HEMA immobilization and a maximum grafting yield of about 0.13% was obtained for a short irradiation time of 12 min with 25% of HEMA monomer. In vitrofibrinogen and fluorescent labeled bovine serum albumin adsorption results indicated that the COC surface can easily be tuned against protein adsorption by controlling the grafting yield. The in vitroplatelet adhesion tests confirmed that the hydroxyl functionality greatly improved the surface hemocompatibility of COC by reducing the number and the degree of activation of the adherent platelets.

Intrinsically Antibacterial Materials Based on Polymeric Derivatives of Eugenol for Biomedical Applications

Infections are the most common cause of biomaterial implant failure representing a constant challenge to the more widespread application of medical implants. This study reports on the preparation and characterization of novel hydrophilic copolymeric systems provided with antibacterial properties coming from eugenol residues anchored to the macromolecular chains. Thus, high conversion copolymers were prepared from the hydrophilic monomer 2-hydroxyethyl methacrylate (HEMA) and different eugenol monomeric derivatives, eugenyl methacrylate (EgMA) and ethoxyeugenyl methacrylate (EEgMA), by bulk polymerization reaction. Thermal evaluation revealed glass transition temperature values in the range 95-58 degrees C following the order HEMA-co-EgMA > PHEMA > HEMA-co-EEgMA and a clear increase in thermal stability with the presence of any eugenyl monomer in the system. In vitro wettability studies showed a reduction of water sorption capacity and surface free energy values with increasing the content of eugenol residues in the copolymer. The antimicrobial activity of copolymeric discs was evaluated by determining their capacity to reduce or inhibit colony formation by different bacterial species. All eugenyl containing materials showed bacteria growth inhibition, this one being higher for the EEgMA derivative copolymers.

Polymethacrylate-type monoliths functionalized with chiral amino phosphonic acid-derived strong cation exchange moieties for enantioselective nonaqueous capillary electrochromatography and investigation of the chemical composition of the monolithic polymer

In situ prepared monolithic poly(glycidyl methacrylate-co-ethylene dimethacrylate) (poly(GMA-co-EDMA)) capillary columns were activated to reactive thiol-monoliths and subsequently functionalized with (S)-N-(4-allyloxy-3,5-dichlorobenzoyl)-2-amino-3,3-dimethylbutanephosphonic acid as chiral selector by radical addition to afford enantioselective strong cation exchanger (SCX) capillary columns (100 microm inner diameter (ID)). These monolithic capillaries were devised for the enantioseparation of chiral bases by nonaqueous and aqueous capillary electrochromatography (CEC) and the results obtained for mefloquine and its tert-butylcarbamate as test compounds were compared to those obtained with particulate silica-based analogs (packed columns). Despite abolishment of nonspecific ionic interactions between the cationic solutes and residual silanols that may diminish separation factors of the silica-based chiral SCX particles, the poly(GMA-co-EDMA)-supported SCX monolith did not, as expected, show better enantioselectivities, which was assumed to be due to detrimental nonspecific interactions between the analytes and the lipophilic polymer backbone. In order to minimize these unfavorable contributions, less lipophilic monoliths were developed by copolymerization of different amounts of the hydrophilic monomer 2-hydroxyethyl methacrylate (HEMA) with GMA and EDMA, leading to GMA-co-HEMA-co-EDMA-terpolymeric monoliths. By this increase of the hydrophilicity of the monolithic support the enantioselectivity of the resultant SCX stationary phase could be enhanced and reached values comparable to the packed silica-based enantioselective SCX capillaries. Additionally, the mobile phase composition and other variables were examined and it could be shown that the separation factors are considerably affected by diverse parameters such as acetonitrile-methanol ratio and type and concentration of the counterion. Mefloquine enantiomers could be separated with alpha-values up to 1.56 and a maximum plate count of ca. 60,000 m(-1) could be achieved.

Biocompatibility of resin-modified filling materials.

Increasing numbers of resin-based dental restorations have been placed over the past decade. During this same period, the public interest in the local and especially systemic adverse effects caused by dental materials has increased significantly. It has been found that each resin-based material releases several components into the oral environment. In particular, the comonomer, triethyleneglycol di-methacrylate (TEGDMA), and the 'hydrophilic' monomer, 2-hydroxy-ethyl-methacrylate (HEMA), are leached out from various composite resins and 'adhesive' materials (e.g., resin-modified glass-ionomer cements [GICs] and dentin adhesives) in considerable amounts during the first 24 hours after polymerization. Numerous unbound resin components may leach into saliva during the initial phase after polymerization, and later, due to degradation or erosion of the resinous restoration. Those substances may be systemically distributed and could potentially cause adverse systemic effects in patients. In addition, absorption of organic substances from unpolymerized material, through unprotected skin, due to manual contact may pose a special risk for dental personnel. This is borne out by the increasing numbers of dental nurses, technicians, and dentists who present with allergic reactions to one or more resin components, like HEMA, glutaraldehyde, ethyleneglycol di-methacrylate (EGDMA), and dibenzoyl peroxide (DPO). However, it must be emphasized that, except for conventional composite resins, data reported on the release of substances from resin-based materials are scarce. There is very little reliable information with respect to the biological interactions between resin components and various tissues. Those interactions may be either protective, like absorption to dentin, or detrimental, e.g., inflammatory reactions of soft tissues. Microbial effects have also been observed which may contribute indirectly to caries and irritation of the pulp. Therefore, it is critical, both for our patients and for the profession, that the biological effects of resin-based filling materials be clarified in the near future.

Photopolymerized 2-Hydroxyethylmethacrylate as a mounting medium preserving immunocytochemical reaction and nuclear counterstain

Immunocytochemical or cytoenzymological techniques often make use of coupling reactions between a substituted naphtol and a diazonium salt. A positive reaction results in an azo dye precipitate. Unfortunately, this precipitate is easily soluble in alcohols and organic solvents. Thus, usual mounting media are not usable and permanent preparations cannot be obtained. A stable mounting medium such as Apathy's syrup can be used, but nuclear counter-staining disappears in a few days. We tested the hydrophilic monomer 2-hydroxyethylmethacrylate, containing various photopolymerizing agents, as a permanent mounting medium. 2–2 Dimethoxy 2-phenyl acetophenone proved to be the most useful photopolymerizer. The cytocentrifugation slides must be dried before mounting to avoid recrystallization artifacts. The azo dye precipitate and nuclear counterstaining can be preserved perfectly long-term. The cost of these media is very low.

Synthesis of uniform microspheres with higher content of 2-hydroxyethyl methacrylate by employing SPG (Shirasu porous glass) emulsification technique followed by swelling process of droplets

Relatively uniform microspheres containing a hydrophilic monomer, 2-hy- droxyethyl methacrylate (HEMA), were prepared by employing a swelling method of uniform seed droplets. A uniform seed emulsion composed mainly of styrene (St) was prepared by the Shirasu porous glass (SPG) membrane emulsification technique; this was mixed with a secondary emulsion composed mainly of HEMA/St or HEMA/MMA (methyl methacrylate) prepared by a homogenizer for swelling. The swollen droplets obtained were polymerized at 757C under a nitrogen atmosphere. The uniform mi- crosphere with a higher content of HEMA was obtained successfully by the swelling method while it failed by a direct emulsification method. The effects of the composition of the oil phase and the inhibitor in the continuous phase on the incorporated fraction of HEMA, the morphology of particles, and monomer conversion were investigated. It was found that the incorporated fraction of HEMA increased with increasing its feed fraction, and more HEMA was incorporated into the microsphere when HEMA/MMA was used as the oil phase of the secondary emulsion rather than HEMA/St. Although the final conversion was very low when the feed fraction of HEMA was higher, it can be increased to more than 80% by using an adequate amount of ethylene glycol dimethacrylate (EGDMA) as a crosslinker and NaNO2 as an inhibitor in the aqueous phase. Various microspheres with different morphologies such as spherical, snow- manlike, and popcornlike were observed, depending on composition of the oil phase. Furthermore, the porous microsphere with a high content of HEMA was obtained by employing hexanol (HA) as a porogen. q 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1325-1341, 1997

Wetting and adhesion of water-borne printing inks on surface-modified polyolefins

Polyolefin films were surface-modified by different methods to improve the wetting and adhesion of water-borne printing inks. Polyethylene (PE) films were treated with corona at various energy levels. Surface-modified PE films were characterized by contact angle measurements and electron spectroscopy for chemical analysis (ESCA). Good wetting was already achieved with treatment at a lower energy level. Various degrees of adhesion were obtained at various degrees of treatment. A hydrophilic monomer, 2-hydroxyethylmethacrylate (HEMA), was polymerized onto the surfaces of polypropylene (PP) with radiation-induced grafting, which was carried out at two different radiation doses. In both cases, a thick, visible layer of polyHEMA was formed on the surface of PP, and satisfactory wetting was already achieved at lower radiation doses. Scanning electron microscopy (SEM) showed that different degrees of roughness were achieved at various radiation doses. Like the case of corona-treated PE, different degrees of adhesion were obtained at different degrees of surface treatment. This study shows that improved wetting alone is not satisfactory for good practical adhesion', regardless of the surface modification method used.

The Viscosity Behavior of ABA-Type Block Copolymer Composed of 2-Hydroxyethyl Methacrylate and Styrene in Organic Solvent Mixture

The ABA-type block copolymer and the random cooligomer composed of a hydrophilic monomer, 2-hydroxyethyl methacrylate (HEMA), and a hydrophobic monomer, styrene (St), were synthesized to study the influence of the hydrophilic and the hydrophobic block chains on the polymer properties in dilute solution. Viscometric measurements were carried out at various temperatures in two solvent mixtures composed of N, N-dimethylformamide (DMF) or ethanol and dioxane which had preferential affinity to one of the block chains. It was found by viscometric measurements that the solution behavior of the ABA-type block copolymer containing a 0.394-mol fraction of HEMA was remarkably different from that of the random cooligomer of the same composition. That is, in each polymer system, the viscosity curves showed maximum values at an optimum composition of the solvent mixture. The peak for the block copolymer, however, shifted to the DMF- or ethanol-rich composition at any one temperature in comparison with that for the random cooligomer. The shift of the peak became large with decreasing temperature. In DMF— dioxane system, especially, the intrinsic viscosity vs. solvent composition curve displayed a cusp at about 0.4-vol fraction of dioxane, suggesting that a conformational transition took place within the block copolymer chain. The cusp smoothed out with decreasing temperature, and changed into a maximum appearing at about 0.2-vol fraction of dioxane.

The influence of hydrophilic and hydrophobic domains on water wettability of 2‐hydroxyethyl methacrylate‐styrene copolymers

AbstractCooligomers and ABA‐type block copolymers composed of a hydrophilic monomer, 2‐hydroxyethyl methacrylate (HEMA), and a hydrophobic monomer, styrene, were synthesized to study the relation between their microstructure and hydrophilic and hydrophobic functions. Films of cooligomers and ABA‐type block copolymers were cast from DMF solutions at 40°C. The wettability, which was determined from the contact angle with water, increased considerably when HEMA mole fraction reached around 0.8 in the cooligomer system and around 0.9 in the ABA‐type block copolymer system. The microstructures of the copolymer films were observed by electron microscopy using the osmium tetroxide fixation technique. The morphologic change in the domain structure was observed at an HEMA mole fraction of about 0.8 in the cooligomer system and about 0.9 in the ABA‐type block copolymer system. It is suggested that hydrophilic and hydrophobic functions are largely influenced by the state of aggregation of each segment, that is, the size and geometry of the hydrophilic and hydrophobic domains.