Synthesis and phosphorescent properties of the copolymers of N-vinylcarbazole,methyl methacrylate and iridium complex

The copolymers containing carbazole unit and iridium complexes, such as (Ir(bpy)₂Cl, Ir(mbpy)₂Cl and Ir(Brbpy)₂Cl, were synthesized via radical copolymerization of N-vinylcarbazole, methyl methacrylate and iridium complex. The synthesized copolymers were characterized by FT-IR, UV-Vis absorption spectroscopy and photoluminescence (PL) spectroscopy, respectively. According to the results, the copolymers (Ir(Brbpy)₂Cl/PVK and Ir(mbpy)₂Cl/PVK) exhibit yellow phosphorescence with an emission peak at around 553 nm under UV-visible light in the solid state. The results also reveal almost complete energy transfer from the host carbazole segments to the guest Ir complex in the copolymer film when the Ir content reaches 1.0 wt.%. The synthesized copolymers are good candidates as blue or yellow phosphorescent materials for PLED applications.     

Synthesis and properties novel polyurethane-hexafluorobutyl methacrylate copolymers

Novel physically crosslinked polyurethane-hexafluorobutyl methacrylate (PU-M) copolymers were prepared by the macroiniferter-controlled radical polymerization method. The chemical structures of the PU-M copolymers were characterized by FT-IR, (1)H-NMR, GPC, DSC, and XPS. The self-assembly and surface properties of the PU-M copolymers have been investigated. The results revealed that PU-M copolymers have good hydrophobility, so the hydrophobility of polyurethane could be easily adjusted by controlling the content of the hydrophobic vinyl monomers. The mechanical evaluation shows that PU-M copolymers exhibit good mechanical properties. The effects of the fluorine content on the surface properties and self-assembly of the PU-M copolymers were investigated. The morphology of the PU-M copolymers' self-assembly was observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM), and the mechanism of self-assembly was investigated. Antimicrobial property of the chlorinated PU-M copolymers against both Escherichia coli and Bacillus subtilis bacteria was examined and showed increase compared to that of pure polyurethane.     

Photoluminescence of fullerene-doped copolymers of methyl methacrylate during laser irradiation

Photoluminescence (PL) intensities of C₆₀-doped poly(methyl methacrylate-co-ethyl acrylate) (P(MMA-co-EA)) and poly(methyl methacrylate-co-methacrylic acid) (P(MMA-co-MAA)), increase gradually during laser irradiation in air. Concomitantly, their PL peaks are broadened and blue-shifted. C₇₀-doped copolymers exhibit a rapid increase in PL intensity soon after the start of laser irradiation, but the PL intensities then decrease to a minimum upon further irradiation. After that, their PL intensities increase again, similar to that of C₆₀-doped copolymers. By analyzing UV-visible spectra, these increases in PL are attributed to the formation of some fullerene oxide-copolymer complex by laser induced photochemical oxidation reactions.     

Thermal degradation behaviors of poly (dimethylsiloxane)-urethane-graft-poly (methyl methacrylate) copolymers based on various diisocyanates

The thermal decomposition behaviors of slightly crosslinked poly(dimethylsiloxane)-urethane-graft-poly(methyl methacrylate) (PDMS-urethane-g-PMMA) copolymers based on two diisocyanates: 2,4-toluene diisocyanate (2,4-TDI) and m-xylene diisocyanate (m-XDI) are discussed. By analyzing the residues of the decomposed copolymers and thermal degradation behaviors of copolymers, it was proposed that poly(dimethylsiloxane) (PDMS) in the copolymers traps free radicals generated from the thermal decomposition of the copolymer and reduces the rate of thermal decomposition. In addition, the crosslinking structure of PDMS can also reduce the evaporation of volatiles from the thermal decomposition process.     

The mechanical properties of PMMA and its copolymers with ethyl methacrylate and butyl methacrylate

The mechanical properties of polymethyl methacrylate and copolymers formed with both ethyl methacrylate and butyl methacrylate were investigated. Six polymers were produced by bulk polymerization, measured for molecular weight and glass transition temperature, T _g and assessed for modulus of elasticity and fracture toughness. Increasing the concentration of ethyl methacrylate or butyl methacrylate resulted in a linear decrease in the glass transition temperature, modulus of elasticity, and fracture toughness. A comparison of testing environments revealed that the modulus of elasticity was reduced when conditioned and tested in water at 37 °C compared to ambient laboratory conditions for all polymers. Similar comparisons of the fracture toughness showed an increase for testing in water at 37 °C; however, this was not significant for the lower T _g compositions. Both modulus of elasticity and fracture toughness were strongly correlated with the glass transition temperature and composition.     

Preparation of hydroxyapatite/poly(methyl methacrylate) and calcium silicate/poly(methyl methacrylate) interpenetrating hybrid composites

Hydroxyapatite/poly(methyl methacrylate) (HAp/PMMA) and calcium silicate/poly(methyl methacrylate) (CS/PMMA) composites were prepared by interpenetrating bulk polymerization of methyl methacrylate (MMA) monomer in porous structures of HAp and CS. The porous HAp and CS templates were prepared by mixing their calcined powders with poly(vinyl alcohol) (PVA) solution, shaping by uniaxial pressing and then firing at 1,100 °C for HAp and 900 °C for CS. The templates were soaked in the solution mixture of MMA monomer and 0.1 mol% of benzoyl peroxide (BPO) for 24 h. The pre-composites were then bulk polymerized at 85 °C for 24 h under nitrogen atmosphere. The microstructures of the composites showed the interpenetrating of PMMA into the porous HAp and CS structures. Thermogravimetric analysis indicated that the PMMA content in the HAp/PMMA and CS/PMMA composites were 13 and 26 wt%, respectively. Weight average molecular weights ( ) of PMMA were about 491,000 for HAp/PMMA composites and about 348,000 for CS/PMMA composites. Compressive strengths of these composites were about 90–131 MPa in which they were significantly higher than their starting porous templates.     

Studies on novel radiopaque methyl methacrylate: glycidyl methacrylate based polymer for biomedical applications

A new class of radiopaque copolymer using methyl methacrylate (MMA) and glycidyl methacrylate (GMA) monomers was synthesized and characterized. The copolymer was made radiopaque by the epoxide ring opening of GMA using the catalyst o-phenylenediamine and the subsequent covalent attachment of elemental iodine. The copolymer was characterized by Fourier transform infrared (FTIR) spectra, energy dispersive X-ray analysis using environmental scanning electron microscope (EDAX), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). X-ray visibility of the copolymer was checked by X-radiography. Blood compatibility and cytotoxicity of the newly synthesized copolymer were also evaluated. The iodinated copolymer was thermally stable, blood compatible, non-cytotoxic, and highly radiopaque. The presence of bulky iodine group created a new copolymer with modified properties for potential use in biomedical applications.     

Quantitative analysis and structure determination of styrene/methyl methacrylate copolymers by pyrolysis gas chromatography

A pyrolysis gas chromatography (Py-GC) method has been developed to study the composition and microstructure of styrene/methyl methacrylate (STY/MMA) copolymers. The composition was quantified by Py-GC using monomer peak intensity. Because of the poor stability of methyl methacrylate oligomers, neither MMA dimer nor MMA trimers were detected under normal pyrolysis conditions. The number-average sequence length for STY was determined by pure and hybrid trimer peak intensities. The number-average sequence length for MMA was determined by using formulas that incorporate composition and the number-average sequence length of STY. This method is a new approach for the investigation of the microstructure of those copolymers that do not produce dimer and trimer peaks upon pyrolysis.     

Processing and properties of poly(methyl methacrylate)/carbon nanofiber composites

Single wall carbon nanotubes, multiwall carbon nanotubes, as well as carbon nanofibers (CNF) are being used for reinforcing polymer matrices. In this study, poly(methyl methacrylate) (PMMA) nanocomposites have been processed by melt blending, containing two different grades (PR-21-PS and PR-24-PS) of CNF manufactured by Applied Sciences Inc. The amount of nanofibers used was 5 and 10% by weight, respectively. The PMMA/CNF composites were processed into 4 mm diameter rods and 60 μm diameter fibers using the small-scale melt processing fiber spinning equipment. At 5 wt% CNF, composite rods as well as fibers show over 50% improvement in axial tensile modulus as compared to the control PMMA rod and fibers, respectively. The reinforcement efficiency decreased at 10 wt% CNFs. The PMMA/CNF nanocomposite fibers also show enhanced thermal stability, significantly reduced shrinkage and enhanced modulus retention with temperature, as well as improved compressive strength. CNF reinforcement efficiency has been analyzed using the modified Cox model.     

The effect of deuteration on the ultrasonic properties of poly(methyl methacrylate)

Room-temperature ultrasonic compressional wave velocity and attenuation measurements have been carried out on commercial poly-methyl methacrylate (PMMA) and fully deuterated PMMA. Deuteration was found to reduce the velocity by 4.4 ± 1.2% which can be completely accounted for by the density change of 8.0%, assuming no changes in atomic force constants or molar volume. The attenuation was 17% higher in the deuterated sample. Making reasonable assumptions about the distribution function for the relaxation times of molecular groupings moving in two-well potentials, the attenuation increase is attributed to a reduction in the attempt frequency for barrier hopping of main chain and/or ester methyl groups.     

Processing and properties of poly(methyl methacrylate)/carbon nano fiber composites

Single wall carbon nanotubes, multi-wall carbon nanotubes, as well as carbon nano fibers (CNF) are being used for reinforcing polymer matrices. In this study, poly(methyl methacrylate) (PMMA) nanocomposites have been processed by melt blending, containing two different grades (PR-21-PS and PR-24-PS) of CNF manufactured by Applied Sciences Inc. The amount of nano fibers used was 5 and 10 wt%, respectively. The PMMA/CNF composites were processed into 4 mm diameter rods and 60 μm diameter fibers using small-scale melt spinning equipment. At 5 wt% CNF, composite rods as well as fibers show over 50% improvement in axial tensile modulus as compared to the control PMMA rod and fibers, respectively. The reinforcement efficiency decreased at 10 wt% CNF. The PMMA/CNF nanocomposite fibers also show enhanced thermal stability, significantly reduced shrinkage and enhanced modulus retention with temperature, as well as improved compressive strength. The CNF reinforcement efficiency has been analyzed using the modified Cox model.     

Thermal and optical properties of poly(methyl methacrylate)/calcium carbonate nanocomposite

The study deals with thermal and optical properties of poly(methyl methacrylate) (PMMA) containing 2wt% calcium carbonate (CaCO₃) nanofiller. It was found that the thermal conductivity increases with increasing temperatures, due to thermal activation of the phonons in the PMMA/CaCO₃ nanocomposite. This enhancement in the thermal conduction is mainly attributed to the heat transferred by lattice vibrations as major contributors and electrons as minor contributors during thermal conduction. The optical properties were investigated as a function of wavelength and photon energy of UV radiation. The optical results obtained were analysed in terms of absorption formula for noncrystalline materials. It was found that the measured optical energy gap for the pure PMMA is greater than the PMMA/CaCO₃ nanocomposite. The width of the energy tails of the localised states was calculated. Adding CaCO₃ nanofiller into PMMA matrix may cause the localised states of different colour centres to overlap and extend in the mobility gap. This overlap may give an evidence for decreasing energy gap when adding CaCO₃ nanofiller in the polymer matrix.     

Swelling behavior of gelatin-g-methyl methacrylate copolymers

Gelatin-methyl methacrylate graft copolymers were prepared with gelatin and methyl methacrylate (MMA). The effect of various reaction parameters on the swelling behavior was investigated systematically, such as the concentration of the monomer, the content of the initiator, reaction time and temperature. In addition, the effect of intercalation of graft copolymers with montmorillonite (MMT) on swelling behavior was studied. The results indicated that the graft copolymerization and intercalation with MMT could greatly reduce the swelling degree of gelatin. The swelling process of the copolymers followed second-order kinetics identical to that of the original gelatin.     

Interactions of chondrocytes with methacrylate copolymers

Copolymers of poly(ethylmethacrylate) (PEMA) and tetrahydrofurfurylmethacrylate (THFMA) have been shown to exhibit potential as a biomaterial for use in cartilage repair. However, the interactions of chondrocytes with the polymer surface is not well understood. A series of novel methacrylate copolymers containing PEMA, THFMA and hydroxyethylmethacrylate (HEMA) were prepared and the ability of these various copolymers to support chondrocytes attachment in vitro has been assessed by the Alamar blue assay for cell number and environmental scanning electron microscopy (ESEM). As the mole fraction of HEMA in PEMA/THFMA/HEMA copolymers increased, chondrocyte attachment to the polymer surface in 24 h decreased. Chondrocytes maintained a rounded morphology and were strongly attached on the THFMA/PEMA polymer surface, but as the mole fraction of HEMA increased the cells present became much smaller with fewer cell to cell interactions. The effect of pre-adsorbing fibronectin on to the polymer surface on cell attachment was assessed both in the presence and absence of serum. Chondrocyte attachment was significantly reduced in serum-free medium. Pre-adsorption of fibronectin on to the copolymer surface substantially increased cell attachment in all cases. In conclusion, chondrocyte attachment and proliferation on these copolymers may be controlled by changes in the polymer surface chemistry and is highly sensitive to the presence of proteins either in the culture media or pre-adsorbed on to the copolymer surface. © 1998 Kluwer Academic Publishers     

Anisotropic properties of aligned SWNT modified poly (methyl methacrylate) nanocomposites

The poly (methyl methacrylate) (PMMA)/single-walled carbon nanotube (SWNT) composites with good uniformity, dispersion and alignment of SWNT were fabricated in an improved figuration process. The semidried mixture was stretched along one direction at a drawing ratio of 50 before it was dried, and then folded along the same direction stretching repeatedly for 100 times. The transmission electron microscopic (TEM) observation demonstrated that SWNT in the PMMA/SWNT composite tends to align in the stretching direction owing to a torque exerting on it in the stretching process. The electrical and mechanical properties of PMMA/SWNT composite were studied as a function of SWNT orientation and concentration. The aligned SWNT modified PMMA/SWNT composite presented highly anisotropic properties. The experimental results showed that the electrical conductivity and mechanical properties of composite rise with the increase of SWNT concentration, and that composite films showed higher conductivity and higher mechanical draw ratios along the stretched direction than perpendicular to it. The thermogravimetric analysis (TGA) revealed that embedding the SWNTs into the PMMA matrix also improves the thermal stability of the composite.     

Poly(methyl methacrylate)–titania hybrid materials by sol–gel processing

Sol–gel derived poly(methyl methacrylate)–titania hybrid materials were synthesized by using acrylic acid or allyl acetylacetone (3-allyl-2,4-pentanedione) as coupling agent. Titanium butoxide modified with acrylic acid (or titanium isopropoxide modified with allyl acetylacetone) was hydrolysed to produce a titania network, and then poly(methyl methacrylate) (PMMA) chains, formed in situ through a radical polymerization, were chemically bonded to the forming titania network to synthesize a hybrid material. Transparent hybrid materials with different contents of titania were achieved. With increase of the titania content, the colours of the products changed from yellow to dark red. The synthesis process was investigated step by step by using Fourier transform–infrared spectroscopy, and the experimental results demonstrated that acrylate or acetylacetonato groups bound to titanium remain in the final hybrid materials. The thermal stability of the hybrid materials was considerably improved relative to pure PMMA. Field emission scanning electron microscopy analyses showed the hybrid materials are porous and pore diameters vary from 10–100 nm. The hybrid materials using allyl acetylacetone as coupling agent exhibited a thermochromic effect that neither pure PMMA nor titania exhibit. This revised version was published online in November 2006 with corrections to the Cover Date.     

Improved thermal properties of graphene oxide-incorporated poly(methyl methacrylate) microspheres

Graphene, a single layer of carbon atoms in a two-dimensional lattice, has attracted considerable attention owing to its unique physical, chemical and mechanical properties. In particular, because of its excellent thermal properties such as high thermal conductivity and good thermal stability, graphene has been regarded as a one of the promising candidates for the reinforcing fillers on the polymer composites field. In this study, we prepared the poly(methyl methacrylate) (PMMA)/graphene oxide (GO) nanocomposite by a simple solution mixing process, and examined the thermal reinforcing effects of GO on a PMMA matrix. Using thermogravimetric analysis, differential scanning calorimeter, and thermal conductivity meter, we investigated the effects of GO on the thermal properties of PMMA/GO nanocomposites. With 3 wt% of GO loading, the glass transition temperature (Tg) of the PMMA/GO nanocomposite were increased by more than 7 degrees C and the thermal conductivity of which also improved 1.8 times compared to pure PMMA.     

Optical properties of polyethylene/styrene-co-methacrylate copolymers IPN-like networks: Effect of different methacrylate styrene co monomers on properties

Low-density Polyethylene (PE) were synthesized with poly[butyl methacrylate (B)-co-styrene (S)], poly(dodecyl methacrylate(D)-co-styrene] and poly(ethyl hexyl methacrylate (EH)-co-styrene] copolymers in order to obtain IPN-like networks. Different S/methacrylate copolymer molar ratios going from 0/100 up to 60/40, a molar percentage of 1.0% of 1,4-butanedioldimethacrylate (b) and 3 wt% of 2,5-dimethyl-2,5-di-(tert-butyl peroxy) hexane (Luperox 101) were used. The samples were analyzed at RT by WAXS, swelling in CCl₄ and mechanical tensile tests. Dynamic-mechanical tests and optical investigations were performed in a temperature range between RT and 180°C. All the IPN types showed optical reversible transitions (transparency-to opacity and vice versa) with varying temperature, due to a refractive index (RI) matching-mismatching of PE and copolymer networks. The copolymer chemical nature as well as its composition affected sensitively most of the analyzed properties.     

Poly(methyl methacrylate) nanocomposites based on TiO2 nanocrystals: Tailoring material properties towards sensing

Nanocomposite materials have been obtained by dispersing organic capped TiO₂ nanocrystals (NCs) with different shape and surface chemistry in poly(methyl methacrylate) (PMMA) as a host medium. Films of the prepared nanocomposites based on TiO₂ NCs have been fabricated by spin coating and morphologically characterized as a function of the preparative conditions. The organic vapor absorption ability of the PMMA/TiO₂ NC based nanocomposites has been then investigated both for spherical and rod-like NCs, and the chemical nature of the coordinating organic molecules has been also varied. The results of the investigation have demonstrated that NC geometry and surface chemistry can modulate the specific absorption characteristics of the modified PMMA in order to absorb different solvent molecules (i.e. acetone, ethanol, propan-2-ol and water). Such features, due to specific interactions between the potential analyte vapors and the functionalized surface of NCs, can effectively be addressed in a controlled and reproducible way, thus offering original opportunities for designing innovative chemical sensors.