Compositional and structural studies of vinylidene chloride/vinyl chloride copolymers by pyrolysis gas chromatography

A pyrolysis gas chromatography approach has been developed to study the composition and structure of vinylidene chloride/vinyl chloride copolymers. The composition and number average sequence length, which reflects the monomer arrangement in the polymer, were calculated using formulas that incorporate the pure trimer peak intensities and hybrid trimer peak intensities. Because of the reactivity difference between vinyl chloride and vinylidene chloride monomers, the structure of the polymer has been further investigated on the basis of the percentage of grouped monomers (i.e., the number average sequence length for vinyl chloride and vinylidene chloride repeat units). For the vinylidene chloride/vinyl chloride copolymer examined in this study, the composition and number average sequence length elucidated from the pyrolysis gas chromatography study are compared to the product composition specification and/or the composition measured by (1)H-NMR.     

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.     

Viscoelastic properties of hybrid copolymers based on methacryloxypropyl-grafted nanosilica and methyl methacrylate

The linear viscoelastic behavior of “model” hybrid materials based on methyl methacrylate and methacryloxypropyl-grafted nanosilica was investigated. As unique features, the materials under study present an excellent dispersion of silica within the polymer matrix and are almost free of uncross-linked chains. In addition, very progressive changes in network architecture are available, resulting from changes in particle diameter, d, volume fraction of filler, Φ, number of methacryloyl units grafted per surface unit of silica particle, n, and nature of the grafting agent. The influence of these parameters on the characteristics of the mechanically active relaxations α and β was examined. Emphasis was put on the storage modulus, E′, on the loss modulus, E′′, and on their dependence on filler volume fraction. E′′ values were shown to simply account for the reduction of the mechanical energy lost within the material, in connection to the occurrence of polymer molecular motions. Analysis of E′ variations as a function of Φ was based on the theoretical models available in the literature to account for the contribution of the spherical filler particles. In the glassy state, Kerner’s and Christensen and Lo’s models yielded comparable results. In the rubbery state, Guth and Gold’s model was shown to prevail on Kerner’s model.     

Kinetics and thermal studies for the copolymerization of styrene and methyl methacrylate by incorporation of mesoporous diatomite

Activators generated by electron transfer (AGET) for atom transfer radical copolymerization (ATRP) was employed to synthesize tailor-made random poly (styrene-co-methyl methacrylate)/mesoporous kieselgur nanocomposites. Some inherent features of the mesoporous kieselgur platelets were studied by nitrogen adsorption/desorption isotherm and transmission electron microscopy images. Conversion and molecular weight determinations were carried out using gas chromatography and size exclusion chromatography respectively. Addition of 3 wt.% mesoporous kieselgur platelets results in increments of conversion from 72 % to 87 % and molecular weight of copolymer chains from 15986 g mol⁻¹ to 18564 g mol⁻¹ respectively; however, polydispersity index values increases from 1.19 to 1.48. Increasing thermal stability of the nanocomposites is demonstrated by thermogravimetric analysis. Differential scanning calorimetry shows an increase in glass transition temperature from 70.6 °C to 75.7 °C by adding 3 wt.% of mesoporous kieselgur platelets.     

Microlenses fabricated by ultraviolet excimer laser irradiation of poly(methyl methacrylate) followed by styrene diffusion

A new technique of microlens array fabrication based on the use of excimer laser radiation is described. Poly(methyl methacrylate) (PMMA) substrates are treated with many low-energy KrF laser pulses and exposed to styrene vapor. The irradiated material swells, producing spherical microlenses that are stabilized by UV polymerization. The chemistry of this process and the optical quality of the lenses are discussed.     

Quantitative determination of sulfonated aliphatic and aromatic surfactants in sewage sludge by ion-pair/supercritical fluid extraction and derivatization gas chromatography/mass spectrometry.

Secondary alkanesulfonate (SAS) and linear alkylbenzene-sulfonate (LAS) surfactants were quantitatively (> 90%) extracted from sewage sludges as their tetrabutylammonium ion pairs using 400 atm of supercritical CO2 for 5 min of static extraction followed by 10 min of dynamic extraction at 80 degrees C. Ion pairs of SAS and LAS quantitatively formed butyl esters in the injection port of the gas chromatograph and were determined by gas chromatography/mass spectrometry without class fractionation of the sewage sludge extracts. Concentrations of SAS and LAS in sludges from five different sewage treatment plants ranged from 0.27 to 0.80 g/kg of dry sewage sluge and from 3.83 to 7.51 g/kg, respectively. Good reproducibility was achieved with RSDs of typically 5% for replicate extractions and analyses. Homologue and isomer distributions of SAS in sewage sludge indicated an enrichment of the more hydrophobic components in sewage sludge during sewage treatment.     

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.     

Headspace analysis of engine oil by gas chromatography/mass spectrometry

This study establishes the rationale necessary for determining the time to change engine oil. This is based on identifying gaseous components in new and used automobile lubricants. Key compounds, so-called "signature", are separated and identified qualitatively by coupled gas chromatography/mass spectrometry. Volatile antioxidants at zero miles and fuel contaminants at low mileage are observed in the headspace of engine oil. Several oxidative degradation components have been positively identified in the used oil, which include the following: acetaldehyde, acetone, butanal, 2-propanol, acetic acid, 2-hexanol, benzoic acid, benzaldehyde, and 1-pentanol. This study strongly suggests that the status of lubricating oil can be determined by the analysis of the gas phase above the oil. Most importantly, it opens the possibility of performing conditional maintenance of the combustion engine based on information obtained from gas sensors.     

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.     

甲基丙烯酸丁酯/苯乙烯共聚物纤维的制备和性能

以过氧化苯甲酰(BPO)为引发荆,采用水相悬浮聚合法合成了甲基丙烯酸丁酯(BMA)/苯乙烯(St)共聚物,将共聚物溶于N,N-二甲基乙酰胺(DMAc)中配制成纺丝溶液,将其用湿法纺丝成形后制备出具有吸附弱极性液态有机物(油品)功能的甲基丙烯酸丁酯/苯乙烯共聚物纤维.用傅里叶红外光谱仪(FTIR)和1H核磁共振波谱仪(NMR)研究了共聚物的化学结构,用热重分析仪(TG)、动态热机械分析仪(DMA).单丝强力仪等对纤维的相关性能进行了分析.结果表明,BMA/St70/30共聚物纤维的性能良好,对煤油.石油醚和庚烷等油品的饱和吸附率分别达到3.7g/g纤维、5.3 g/g纤维和4.1 g/g纤维.     

聚氨酯/聚甲基丙烯酸甲酯/有机蒙脱土纳米复合材料的制务、结构与性能

首次将插层纳米复合技术与互穿聚合物网络（IPN）技术相结合,通过同步插层聚合法制备了聚氨酯/聚甲基丙烯酸甲酯/有机蒙脱土（PU/PMMA/OMMT）纳米复合材料.XRD、SEM、TGA等研究表明,在聚氨酯/有机蒙脱土（PU/OMMT）体系中蒙脱土以40～700 nm的团聚体不均匀地分散在聚氨酯基体中,且部分蒙脱土被插层,其层间距增加了0.95nm,体系为插层型纳米复合材料.PU/PMMA/OMMT体系中蒙脱土以20～80nm的粒子分布于聚合物基体中,且蒙脱土的插层效果显著,是PU/OMMT体系的2.5倍,形成了插层型纳米复合材料.同时,蒙脱土的加入使得聚氨酯和聚甲基丙烯酸甲酯的互穿聚合物网络（PU/PMMA-IPN）体系中PU相与PMMA相间相分离更明显,塑性相畴粒子尺寸显著增加,且各相中两组分相互作用加强,分布更均匀.PU/PMMA/OMMT纳米复合材料的热稳定性高于其他材料.同时对其力学性能进行了研究,发现其力学性能明显优于聚氨酯、基于聚氨酯和PU/PMMA-IPN和PU/OMMT纳米复合材料.     

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.