Swelling properties of copolymeric hydrogels prepared by gamma irradiation

Crosslinked xerogels in the form of rods have been prepared to > 99.9% conversion by the γ-ray initiated copolymerization in vacuo ob n-butyl acrylate (BA) with N-vinyl-2-pyrrolidone (VP) in the presence and absence of a crosslinking agent. Thin (about 0.5 mm) disks were swollen in water at 21°C, the final equilibrium swelling being the true water content only for copolymers of high BA content. At low-medium BA content, swelling was accompanied by the release of a small water-soluble fraction, leading to a slightly reduced apparent value for the water content. True water contents could be obtained more rapidly by prior Soxhlet extraction with boiling water. For xerogels containing > about 75% VP by weight, the resultant hydrogels had water contents > about 80%. The influences of dose, dose rate copolymer composition, and concentration of crosslinker on the water content, sol fraction, and extension ratio were investigated. A high level of reproducibility in properties of the hydrogels was obtained by numerous replicate experiments. The feasibility of scaling up the preparation to produce long (60 cm) xerogel rods of uniform properties has been demonstrated. For these copolymers, swelling in several common organic solvents generally exceeds that in water.     

Aluminum triflate-cocatalyzed radical copolymerization of styrene and ethyl acrylate

Polymer Bulletin - Various random copolymers, poly(styrene-co-ethyl acrylate), were synthesized by free radical bulk copolymerization cocatalyzed by aluminum triflate (Al(OTf)3). The experimental...     

Preparation and copolymerization of divalent metal salts of ethylene glycol–methacrylate–maleate

Divalent metal salts of ethylene glycol–methacrylate–maleate (EMM) were prepared by the reaction of EMM and divalent metal ions. The divalent metal salts obtained, except for the Ba salt, have melting points which decrease in the order Pb > Ca > Cd > Mg > Zn. The Mg and Ca salts were selected for the copolymerization with MMA, styrene (St), and hydroxyethyl methacrylate. In the copolymerization, the rates of copolymerization increased markedly as the concentration of metal salts increased. Moreover, the systems containing MMA copolymerized more rapidly than those containing St. As for the physical properties of the copolymers obtained, heat distortion temperature, compressive strength, and Rockwell hardness were improved by introducing metal salts into the polymers, and tensile, flexural, and impact strengths are also able to be improved by selecting the most suitable concentration of metal salts according to the species of metal salts and vinyl monomers. Generally, Mg is more effective than Ca in improving the physical properties of the copolymers. Moreover, TGA and boiling water resistance of the copolymers are also discussed.     

Synthesis and in situ functionalization of microfiltration membranes via high internal phase emulsion templating

The continuous phase of high internal phase emulsions (HIPEs) can be polymerized to produce highly porous materials, known as polyHIPEs. The aim of this work was to synthesize polyHIPE microfiltration membranes having a hydrophobic bulk and a hydrophilic surface to enhance their performance. Therefore, in situ functionalization was performed through interfacial copolymerization of a hydrophobic monomer (butyl acrylate) in the continuous phase with a hydrophilic monomer (sodium acrylate) in the disperse phase. The functionalization of polyHIPEs was studied by using conductometric titration and Fourier transform IR spectroscopy. We show that the surface charge density of poly(butyl acrylate)‐based polyHIPEs can be controlled by varying the concentration of sodium acrylate in the disperse phase. PolyHIPE microfiltration membranes have higher intrinsic permeability (around 1.31 × 10^?8 m²) in comparison to conventional microfiltration membranes. The interfacial copolymerization of sodium acrylate increases the permeability of microfiltration membranes. In addition, the rejection of polyHIPE microfiltration membranes was studied for the separation of microalgae. © 2019 Society of Chemical Industry     

Facile fabrication method of hydrophobic-associating cross-linking hydrogel with outstanding mechanical performance and self-healing property in the absence of surfactants

A cationic surfactant monomer, dimethyldodecyl(2-acrylamidoethyl)ammonium bromide (AMQC₁₂) was synthesized. A family of hydrophobic-associating cross-linking hydrogels (HAC-gels) fabricated via the self-assembly of amphiphilic multiblock copolymers of acrylamide and AMQC₁₂ can be synthesized by free-radical aqueous solution micelle copolymerization in the absence of surfactants using the one-pot method. The HAC-gels possessed outstanding mechanical performance, with optimal tensile strength, compressive strength, and elongation at break of 250 kPa, 14 MPa, and 1850%, respectively. Meanwhile, the HAC-gels exhibited self-healing property, and tetrahydrofuran (THF) significantly accelerated their self-healing process. The recovery hysteresis of hydrophobic-associating hydrogels prepared in the presence of surfactants can be eliminated because of homogeneity of the hydrogel network and the dynamic and mobile properties of physical cross-linking junctions. Investigations on the mechanical property and structure evolution of hydrogels revealed that the hydrophobic-associating interaction was the driving force of self-assembly of amphiphilic multiblock copolymers. Furthermore, spherical micelles and macroscopic cross-linking network can be easily switched reversibly by regulating copolymers concentration.     

Synthesis and properties of silk sericin-<Emphasis Type="Italic">g</Emphasis>-poly(acrylic acid-co-acrylamide) superabsorbent hydrogel

A novel superabsorbent hydrogel has been synthesized with the crosslinking graft copolymerization of acrylic acid (AA) and acrylamide onto the chain of silk sericin. Potassium persulfate (KPS)–sodium sulfite (NaHSO₃) as redox initiation system and N,N′-methylenebisacrylamide (MBA) as crosslinker were used. The structure of the product characterized by Fourier transform infrared absorption spectroscopy and the surface morphology of the hydrogel were observed by scanning electron microscopy. The certain parameters of the graft copolymerization including the monomer, the initiator, the crosslinker concentration, neutralization degree of AA, reaction temperature, and time were systematically optimized to achieve a hydrogel with maximum swelling capacity (2150 g/g). The optimal conditions were initiator 8 mmol/L, MBA 2.5 mmol/L, neutralization degree of AA 75%, reaction temperature 55 °C, and time 6 h. The swelling ratio in salt solutions was also determined (in 0.9% NaCl aqueous solution: 98 g/g). In addition, the swelling capability of the hydrogel was measured in solutions with pH ranged from 1 to 13. The synthesized hydrogel exhibited a pH-dependent character. Water absorbency of the product in aqueous chloride salt solutions has the Na⁺ > Ca²⁺ > Mg²⁺ > Al³⁺ order in the investigated concentration.     

Preparation and copolymerization of divalent metal salts of ethylene glycol–methacrylate–phthalate

Divalent metal salts of ethylene glycol–methacrylate–phthalate (EMP) were prepared by the reaction of EMP and divalent metal ions in aqueous solution. The divalent metal salts obtained, except for the Pb salt, have melting points which decrease in the order of Ca > Ba > Mg > Zn > Cd salt. The Zn and Cd salts are fairly soluble in most organic solvents. Therefore, the Zn salt and Cd salt were selected for the copolymerization with MMA, styrene (St), and hydroxyethyl methacrylate (HEMA). In the copolymerization, the rates of copolymerization increased markedly as the concentration of metal salts increased. Moreover, the systems containing MMA copolymerized more rapidly than those containing St. As for the physical properties of the copolymers obtained, compressive strength and Rockwell hardness were improved by introducing metal salts into the polymers; and heat distortion temperature and tensile and flexural strengths were also improved by selecting the most suitable concentration of metal salts according to the species of metal salts and vinyl monomers. The TGA and the boiling water resistance of the copolymers were also discussed.     

Synthesis and characterization of polytriphenylamine based graft polymers for photorefractive application

Novel graft copolymers, PTPA-g-PEAs containing poly(triphenylamine) (PTPA) backbone and poly(ethyl acrylate) (PEA) branches were synthesized by the oxidative coupling polymerization of triarylamine monomers followed by grafting of ethyl acrylate via an atom transfer radical polymerization (ATRP). Photorefractive (PR) composites based on the graft copolymers showed good static PR properties and fast response time under moderate conditions. The highest diffraction efficiency (19.7% at 45 V/μm) was observed with the composite containing the graft polymer with 18 mol% of graft density and 27 wt% of PTPA. And the fastest response (8 ms at 50 V/μm) was achieved when PTPA content was 68 wt%.     

Utilization of gold tailings for the construction of foamed ceramics used in external insulation buildings

The utilization of gold tailings and bentonite as raw materials for prepared foamed ceramic was studied. The effects of boric acid and titanium dioxide content on the properties and microstructures of foamed ceramic were studied from the aspects of bulk density, compressive strength, bending strength, phase composition, and micromorphology. These results show that the synergistic effect of boric acid and titanium dioxide leads to the crystallization of quartz, which enhanced the compressive strength and bending strength and decreased the thermal conductivity of foamed ceramics, while the bulk density increases gradually with the addition of titanium dioxide. Taking into account all of these properties, the optimal results are as follows: bending strength of 1.111 MPa, compressive strength of 1.165 MPa, bulk density of 0.258 g/cm³, the porosity of 81.89%, the thermal conductivity of 0.088 (W/(m⋅K)). This study indicated that gold tailings are a promising candidate for the preparation of foamed ceramics used as external insulation building materials.     

Swelling behavior of gelatin‐g‐poly(butyl acrylate) copolymers

Gelatin‐g‐poly (butyl acrylate) copolymers were prepared with gelatin and butyl acrylate. The effects of various reaction parameters, including the concentration of the monomer, the concentration of the initiator, the concentration of gelatin, the reaction time, and the temperature, on the swelling behavior were studied systematically. In addition, the effect of the intercalation of graft copolymers with montmorillonite on the swelling behavior was investigated. The results indicated that the graft copolymerization and intercalation with montmorillonite could greatly reduce the swelling degree of gelatin. The swelling process of the copolymers followed second‐order kinetics identical to those of the original gelatin. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1033–1037, 2005     

Preparation of syntactic carbon foam

A pressure molding technique for preparing syntactic carbon foam having high compressive strength and low bulk density (> 500 lb/in² at 0·18 g/cm³) is described. The use of hollow phenolic resin and carbon microspheres of various types, particle size, and wall thickness, along with different carbonaceous binder materials, solvents, and molding pressures prior to coking at 900°C were some of the major variables investigated in relation to compressive strength and density characteristics of the syntactic carbon foams.     

A novel well-defined amphiphilic diblock copolymer containing perfluorocyclobutyl aryl ether-based hydrophobic segment

A series of well-defined binary hydrophilic-fluorophilic diblock copolymers were synthesized by successive atom transfer radical polymerization (ATRP) of methoxylmethyl acrylate (MOMA) and 4-(4′-p-tolyloxyperfluorocyclobutoxy)benzyl methacrylate (TPFCBBMA) followed by the acidic selective hydrolysis of the hydrophobic poly(methoxymethyl acrylate) (PMOMA) segment into the hydrophilic poly(acrylic acid) (PAA) segment. ATRP of MOMA was initiated by 2-MBP at 50 °C in bulk to give two different PMOMA homopolymers with narrow molecular weight distributions (M_w/M_n ≤ 1.15). PMOMA-b-PTPFCBBMA well-defined diblock copolymers were synthesized by ATRP of TPFCBBMA at 90 °C in anisole using Br-end-functionalized PMOMA homopolymer as macroinitiator and CuBr/PMDETA as catalytic system. The final PAA-b-PTPFCBBMA amphiphilic diblock copolymers were obtained via the selective hydrolysis of PMOMA block in dilute HCl without affecting PTPFCBBMA block. The critical micelle concentrations (cmc) of PAA-b-PTPFCBBMA amphiphilic copolymers in aqueous media were determined by fluorescence spectroscopy using pyrene as probe and these diblock copolymers showed different micellar morphologies with the changing of the composition.     

Preparation and characteristics of porous anorthite ceramics with high porosity and high-temperature strength

High-temperature properties including compressive strength, thermal shock behavior, and thermal conductivity of porous anorthite ceramics with high specific strength were tested and analyzed. The results showed that the prepared materials merit high-temperature compressive strength, thermal stability, and conductivity. With the appropriate fabrication parameters, even though containing 0.33 g/cm³ bulk density and 88.2% porosity, its compressive strength could reach 2.03 MPa at 1000°C, 147% of that at room temperature; the residual strength ratio kept as 114.7% after a thermal shock at 1200°C. The X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) showed that anorthite grains refinement and intergranular voids filling by liquid phase were main factors for the high strength. From room temperature to 1200°C, its thermal conductivity only varied from 0.085 to 0.258 W·(m·K)⁻¹. High porosity, a large number of nanoregions in anorthite grains and amorphous phase in grain boundary were main reasons for low thermal conductivity.     

Preparation and characterization of foam glass from waste container glasses and water glass for application in thermal insulations

Glass foams are modern developed building materials which are now favorably competing with conventional materials for applications in thermal insulation. In this study, glass foams are synthesized solely from waste container glasses of mixed colors using sodium silicate (water glass) as foaming agent. Several glass foams of 150 × 150 × 30 mm were prepared from waste glasses of 75 μm, 150 μm and 250 μm size with addition of 15 wt % sodium silicate respectively and pressed uniaxially under a pressure of 10 MPa. The prepared glass foams were then sintered at temperatures of 800 °C and 850 °C respectively. Tests such as bulk density, estimated porosity, flexural strength, compressive strength and microstructure evaluation were used to assess the performance of the developed glass foams. The results showed that with increasing temperature and grain sizes, the percent porosity of the developed foams increased while the bulk density decreased. The microstructure evaluation showed that the finer the grain sizes used, the more homogenized are the pores formed and the higher the temperature, the larger the pores but are mostly closed. Both compressive and flexural strength were found to decrease with grain sizes and higher temperatures. The thermal conductivities of all the developed foam glasses satisfy the standard requirement to be used as an insulating material as their thermal conductivities did not exceed 0.25 W/m.K.     

Microstructure and properties of porous anorthite/mullite whiskers ceramics with high porosity

Porous anorthite/mullite whiskers ceramics with high porosity (>91%) and high strength (>0.45 MPa) have been successfully prepared by foam gel-casting method. Effects of extra mullite whiskers on properties including thermal conductivity and compressive strength at different temperatures were investigated and discussed in terms of microstructure observed through SEM and TEM. The results showed that the addition of extra mullite whiskers in certain content could effectively reduce thermal conductivity, improve the compressive strength both at room and high temperature at same time. When the mullite whiskers content was 20 mol%, the porosity was as high as 91.6 ± 0.19%, the thermal conductivity was low to 0.034 ± 0.003 W/(m·K), and the compressive strength at 1000°C was high to 0.64 ± 0.11 MPa three times to the pure one. Small pores, small grains, and more phase interface or grain boundary caused by the addition of extra mullite whiskers were the main factors for low thermal conductivity. Meanwhile, small pores, closely bonded small grains, and the stable three-dimension network formed by mullite whiskers helped to improve strength.     

Effect of atom transfer radical polymerization macroinitiator on properties of poly(meth)acrylate-based pentablock type of thermoplastic elastomers

We report well controlled synthesis of novel tri-component [polyisobutylene (PIB), poly(n-butyl acrylate) (PnBA) and poly(methyl methacrylate) (PMMA)] pentablock copolymers (PMMA-b-PnBA-b-PIB-b-PnBA-b-PMMA) by Atom Transfer Radical Polymerization (ATRP) using PIB as a macroinitiator. The surface properties (hydrophobicity, in vitro oxidative stability and cellular interaction) and the bulk properties (phase separation and mechanical properties) of the PIB-containing pentablock copolymers were compared with PMMA-b-PnBA-b-PDMS-b-PnBA-b-PMMA (where PDMS = polydimethylsiloxane) and conventional PMMA-b-PnBA-b-PMMA copolymers synthesized by PDMS and PnBA macroinitiators respectively. It is revealed that type of ATRP macroinitiator (with low glass transition temperature) influences the properties of resultant pentablock copolymers in terms of phase separation, mechanical properties in vitro oxidative stability, cytocompatibility and cell proliferation. Pentablock copolymers synthesized by PIB macroinitiator exhibited superior overall properties compared to pentablock copolymers synthesized by PDMS macroinitiator and neat triblock copolymer synthesized by PnBA macroinitiator. Among the copolymers tested, one with composition PIB:PnBA:PMMA = 10:64:26 (w/w) exhibited best mechanical property, oxidative stability and cytocompatibility. The newly designed PIB-containing pentablock copolymer may be useful where softness, flexibility, processability and biostability/cytocompatibility are desired.     

Heterogeneous Structures in the Synthesis of Hydrophobic Lauryl Acrylate-Styrene-Ethylene Glycol Dimethacrylate Copolymer Particles

Novel crosslinked hydrophobic lauryl acrylate-styrene-ethylene glycol dimethacrylate copolymer particles were synthesized with heterogeneous structures by radical suspension copolymerization with benzoyl peroxide as the initiator. Ethylene glycol dimethacrylate was used as a crosslinking agent; toluene, cyclohexanol, 1-octanol and liquid paraffin were used as porogens. The effects of the crosslinking monomer and porogens on the morphologies of the copolymer microspheres were investigated. The copolymers were characterized by FTIR, SEM and swelling in toluene. Permanent pores remained in the dried polymeric particles prepared with nonsolvating porogens at certain crosslink densities as indicated by SEM pictures. The results of swelling revealed that 1-octanol was the most effective porogen, leading to the LA-S-EGDMA copolymer particles with maximum porosity and optimized spheric morphology. Furthermore, lower crosslink density and higher porogen contents promote the formation of porous morphology.     

Benzo[1,2-b:4,5-b′]dithiophene-based copolymers applied in bottom-contact field-effect transistors

Three copolymers of benzo[1,2-b:4,5-b′]dithiophene and 3,3′-bis(alkyl)-5,5′-bithiophene (dodecyl, tetradecyl and hexadecyl side chains) have been synthesized through Stille copolymerization. The polymers have number-average molecular weights over 20 kg/mol, are well-packed in the bulk and thin film, and possess an ionization potential of −5.1 eV in thin film, which offers stability versus oxidation in environmental conditions. The thin film packing of the polymer with dodecyl side chains leads to an excimeric emission upon excitation, which is not observed for longer side chain lengths. The presence of the dimers responsible for this excimer formation results in a device performance improvement as well. Field-effect transistors fabricated from these copolymers have On/Off ratios >10⁷, equal saturation and linear hole mobilities above 10⁻² cm²/Vs, almost no hysteresis and turn-on voltages around 0 V in bottom-contact devices.     

偏光片用丙烯酸酯压敏胶的制备与研究

采用不同的丙烯酸酯单体,应用溶液聚合方法制得了不同性质的丙烯酸酯共聚物,并以该类丙烯酸酯共聚物制得偏光片用压敏胶,探讨了对压敏胶性能产生影响的各种因素。得到初粘性、剥离强度较佳的偏光片用丙烯酸酯压敏胶。     

Structure and properties of Al2O3-bonded porous fibrous YSZ ceramics fabricated by aqueous gel-casting

To meet requirements for high porosity and high strength, novel aqueous gel-casting process has been successfully developed to fabricate Al₂O₃-bonded porous fibrous YSZ ceramics with ρ-Al₂O₃ and YSZ fibers as raw materials. Microstructure, phase composition, apparent porosity, bulk density, thermal conductivity, and compressive strength of fabricated porous ceramics were investigated, and effects of fiber content on properties were discussed. According to results, bird nest 3D mesh with interlaced YSZ fibers and Al₂O₃ binder was formed, ensuring the ability to obtain high performance, lightweight ceramics. An increase in the number of YSZ fibers led to more complex interlaced arrangement of fibers and denser network structure of porous ceramics at retaining their stability. Furthermore, their apparent porosity and bulk density increased, whereas thermal conductivity and compressive strength decreased with increasing the fiber content. In particular, comparatively high porosity (71.1–72.7%), low thermal conductivity (0.209–0.503 W/mK), and relatively high compressive strength (3.45–4.24 MPa) were obtained for as-prepared porous ceramics, making them promising for applications in filters, thermal insulation materials, and separation membranes.