Graft copolymers of poly(methyl methacrylate) backbone and poly(propylene oxide-b-ethylene oxide) branches

Summary Two mono-functional macromonomers of poly (propylene oxide-b-ethylene oxide) were synthesized by reaction with methacryloyl chloride. The macromonomers have the same molecular weight and ratio of ethylene oxide and propylene oxide sequences. The reactive methacrylate group can be linked to the ethylene oxide (BuPPOPEO) or to the propylene oxide (BuPEOPPO). These macromonomers showed self-gelling in one week even at low temperature and under a dry atmosphere. Graft copolymers were obtained by reaction of these macromonomers with methyl methacrylate upon free-radical initiation and they were characterized by GPC, VPO, IR and ¹H NMR spectra.     

Solution behavior of graft copolymers of poly(methyl methacrylate) backbone and poly(propylene oxide-b-ethylene oxide) branches: effect of structure and composition

Summary The effect of structure and composition of poly(methyl methacrylate) (PMMA) main chain and poly(propylene oxide-b-ethylene oxide) (PPO-b-PEO) graft chain on solution behavior was evaluated. Separated samples of homopolymers were also analysed to provide comparisons. The solutions were prepared by dissolving the sample in selective mixtures of tetrahydrofuran (THF) and hexane. The polymer solutions were submitted to viscometric measurements as function of the solvent composition. The ratio of ethylene oxide/propylene oxide (EO/PO) units determines the modification in molecular conformation of the (PPO-b-PEO) block copolymers as function of the solvent composition. The macromolecular structure is the most important factor on the graft copolymers behavior. The structure in which ethylene oxide is linked to the main chain provides higher interaction between graft copolymers and solvent (THF/hexane).     

Surface modification of poly(vinyl chloride) with poly(methyl methacrylate)/poly(dimethyl siloxane) graft copolymers

X-ray photoelectron spectroscopy is used to study the surface segregation of siloxane in dilute blends of poly(methyl methacrylate)/poly(dimethyl siloxane) graft copolymers in poly(vinyl chloride)(PVC). The graft copolymers are found to be extremely efficient surface modifiers, which form, when added in amounts of 0.5% or more, a continuous siloxane overlayer on the surface of PVC. © 1995 John Wiley & Sons, Inc.     

Stereocomplex formation in polybutadiene-syndiotactic poly(methyl methacrylate) block copolymers blended with isotactic poly(methyl methacrylate)

Summary The process of stereocomplexation in blends of isotactic poly(methyl methacrylate)s and polybutadiene-syndiotactic poly(methyl methacrylate) diblock copolymers was studied by differential scanning calorimetry as a function of molar mass of the constituents, annealing time and temperature. The amount of complex formed is dependent on these three parameters, while the temperature of decomposition of the complex is only dependent on the annealing temperature. Complex formation can be observed in blends containing a copolymer with a very low molar mass syndiotactic poly(methyl methacrylate) block (Mn=700). In contrast to homopolymer blends, for which two endotherms of decomposition were generally reported, only one endotherm is observed for copolymer-homopolymer blends. This behavior is attributed to the elastomer block.     

Synthesis and characterization of starch‐poly(methyl methacrylate) graft copolymers

The graft copolymerization was carried out by methyl methacrylate with starch in which azobisisobutyronitrile was used as an initiator. The grafting reactions were carried out within a 65–95°C temperature range, and the effect of the monomer, initiator concentrations, and the amount of starch on the graft yield were also investigated. The maximum graft yield was obtained at a azobisisobutyronitrile concentration of 2.0 × 10^?3 mol/L. The overall rate activation energy of the reaction was found to be 89.42 kJ/mol. The grafted starches were characterized with infrared spectroscopy, scanning electron microscopy, and thermogravimetry. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 53–57, 2002     

Thermal stability of poly(methyl methacrylate)

Summary The average solid-state molecular structures of end-groups generated through chain termination reactions in the polymerization of methyl methacrylate have been derived from published crystallographic data. Evidence is provided for the reduced stability of the head-head chain-termination configuration and in support of the postulate that it is a preferred site of chain scission. Comparable evidence for the unsaturated end group has not been found.     

Synthesis of poly(methyl methacrylate)-g-poly(dimethyl siloxane) graft copolymers via a miniemulsion process

Summary In this article, we describe the synthesis of a PMMA-g-PDMS graft copolymer via a miniemulsion process. A highly hydrophobic PDMS macromonomer was copolymerized in the presence of MMA. Latex particles were obtained with a high yield and a complete incorporation of the macromonomer by using AIBN as initiator, SDS as a surfactant and a PMMA-b-PEO block copolymer as a cosurfactant, with a given amount of methanol in order to reduce the interfacial tension. The characterization of the resulting latex by ¹H NMR and QELS evidenced the interest of such a process in order to copolymerize monomers with very different solubilities and to obtain directly a graft copolymer in aqueous dispersion. Received: 12 March 2001/ Revised version: 15 September 2001/ Accepted: 15 September 2001     

Synthesis and characterization of amphipathic poly(methyl methacrylate)-b-poly(ethylene oxide) diblock copolymers

Summary This paper describes the synthesis and characterization of amphipathic diblock copolymers of poly(methyl methacrylate) (PMMA) and poly(ethylene oxide) (PEO). The synthesis involved the coupling of acyl chloride-terminated PMMA block with methoxy poly(ethylene oxide) (MPEO). Carboxylic acid chloride-terminated PMMA was generated by treating with thionyl chloride the parent carboxylic PMMA, which was prepared by free radical polymerization of methyl methacrylate (MMA) using benzoyl peroxide (BPO) as the initiator and -mercaptopropionic acid (MPA) as the chain transfer agent. The proposed mechanism of MMA polymerization is in good agreement with the experimental results which indicate that as a side reaction nonfunctional (aromatic) counterpart is produced in a small quantity. The coupling of the acyl chloride-terminated PMMA with MPEO was quantitative.     

Syntheses of poly(methyl methacrylate)/poly(dimethyl siloxane) graft copolymers and their surface enrichment of their blend with acrylate adhesive copolymers

Several types of poly(methyl methacrylate)/poly(dimethyl siloxane) graft copolymers (PMMA‐g‐PDMS) were synthesized using macromonomer technology. Three types of PMMA‐g‐PDMS with different PDMS chain length were obtained. The effect of siloxane chain length on surface segregation of PMMA‐g‐PDMS/poly(2‐ethylhexyl acrylate‐co‐acrylic acid‐co‐vinyl acetate)[P(2EHA‐AA‐VAc)] blends was investigated. The blends of PMMA‐g‐PDMS with P(2EHA‐AA‐VAc) showed surface segregations of PDMS components. The surface enrichments of PDMS in the blends depended on the PDMS chain length, significantly. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1736–1740, 2002     

Thermal expansion of irradiated poly(methyl methacrylate)

The thermal expansion coefficient of irradiated poly(methyl methacrylate) is measured in the temperature range 80–350K using a three-terminal capacitance technique. The samples are irradiated with gamma-rays from a ⁶⁰Co source in air at room temperature. The infra-red spectra are taken to indicate radiation-induced changes. The thermal expansion coefficient of poly(methyl methacrylate) is found to increase with radiation dose, the increase being larger at higher temperatures. This has been explained as due to the relative increase in the van der Waals interaction caused by radiation-induced degradation.     

Synthesis and characterization of amphiphilic graft copolymers with hydrophilic poly(acrylic acid) backbone and hydrophobic poly(methyl methacrylate) side chains

A series of well-defined amphiphilic graft copolymers containing hydrophilic poly(acrylic acid) backbones and hydrophobic poly(methyl methacrylate) side chains were synthesized by successive atom transfer radical polymerization followed by the selective hydrolysis of poly(methoxymethyl acrylate) backbone. Grafting-from strategy was employed for the synthesis of graft copolymers with narrow molecular weight distributions. Hydrophobic side chains were connected with the backbone through stable C-C bonds instead of ester connections. The backbone can be easily hydrolyzed to poly(acrylic acid) with HCl without affecting the hydrophobic side chains. The amphiphilic graft copolymers can form stable micelles in water. The critical micelle concentration was determined by fluorescence spectroscopy. The micellar morphologies were found to be vesicles by transmission electron microscopy and changed to spheres with the addition of NaCl.     

Miscibility of poly(methoxymethyl methacrylate) and poly(methylthiomethyl methacrylate) with poly(methyl methacrylate)

Summary Poly(n-propyl methacrylate) is known to be immiscible with poly(methyl methacrylate) (PMMA). However, we have found that poly(methoxymethyl methacrylate) is miscible with PMMA, indicating the importance of ether oxygen atoms in achieving miscibility. On the other hand, poly(methylthiomethyl methacrylate) is immiscible with PMMA.     

表面修饰氧化石墨烯纳米带增强PMMA的研究

以多壁碳纳米管(MWNTs)为原料,使用纵向氧化切割法制备了氧化石墨烯纳米带(GONR),通过物理吸附作用制备了聚醚型苯并咪唑(OPBI)非共价修饰GONR(FGONR)。采用溶液浇注法制得了聚丙烯酸甲酯(PMMA)/FGONR复合材料薄膜,对FGONR及其PMMA复合材料的结构与性能进行了研究,同时对比了以MWNTs,GONR,OPBI改性MWNTs(FCNTs)增强的PMMA复合材料的力学性能。结果表明:OPBI成功地物理吸附到GONR的表面,且FGONR在PMMA中具有良好的分散性能;在PMMA/FGONR复合材料中,当FGONR的质量分数为0.5%时,复合材料的拉伸强度达到49.50 MPa,杨氏模量达到2.27 GPa,其增强效果比MWNTs,GONR,FCNTs的要好,FGONR有望作为制备高性能复合材料的一种良好的纳米填料。     

Synthesis and properties of polycarbonate‐poly(methyl methacrylate) graft copolymers by polycondensation of macromonomers

Polycarbonates (PCs) having poly(methyl methacrylate)s (PMMAs) as graft chains were prepared by the polycondensation of PC oligomers bearing chloroformate groups as the end groups with dicarboxyl‐terminated PMMA macromonomers, which were prepared by the radical polymerization of methyl methacrylate in the presence of thiomalic acid as a chain transfer. The resulting PC‐PMMA graft copolymers were transparent in comparison with PC/PMMA blend polymers, and had higher Vickers hardness than blend polymers when both of them had the same PMMA content. According to the results of multiple regression analysis, the improvement of Vickers hardness was conducive to length (46%) and number (37%) of PMMA branches. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2670–2675, 2001     

Structure-property behavior of poly(dimethylsiloxane) based segmented polyurea copolymers modified with poly(propylene oxide)

Poly(propylene oxide) (PPO) was incorporated in a controlled manner between poly(dimethylsiloxane) (PDMS) and urea segments in segmented polyurea copolymers and their solid state structure-property behavior was investigated. The copolymers contained PDMS segments of MW 3200 or 7000 g/mol and an overall hard segment content of 10-35 wt%. PPO segments of MW 450 or 2000 g/mol were utilized. Equivalent polyurea copolymers based on only PDMS as the soft segment (SS) component were used as controls. The materials (with or without PPO) utilized in this study were able to develop microphase morphology as determined from dynamic mechanical analysis (DMA) and small angle X-ray scattering (SAXS). DMA and SAXS results suggested that the ability of the PPO segments to hydrogen bond with the urea segments results in a limited inter-segmental mixing which leads to the formation of a gradient interphase, especially in the PPO-2000 co-SS containing copolymers. DMA also demonstrated that the polyureas based on only PDMS as the SS possessed remarkably broad and nearly temperature insensitive rubbery plateaus that extended up to ca. 175 °C, the upper temperature limit depending upon the PDMS MW. However, the incorporation of PPO resulted in more temperature sensitive rubbery plateaus. A distinct improvement in the Young's modulus, tensile strength, and elongation at break in the PPO-2000 and PDMS-7000 containing copolymers was observed due to inter-segmental hydrogen bonding and the formation of a gradient interphase. However, when PPO was incorporated as the co-SS, the extent of stress relaxation and mechanical hysteresis of the copolymers increased relative to the segmented polyureas based on the utilization of only PDMS as the soft segment component.     

Preparation and characterization of graft copolymers of methyl methacrylate and poly(n-hexyl isocyanate) macromonomers

Living poly(n-hexyl isocyanate) (PHIC) was deactivated with methacryloyl chloride to produce methacryl-terminated poly(n-hexyl isocyanate) (PHIC-MA) rodlike macromonomers. Radical copolymerization of methyl methacrylate (MMA) with PHIC-MA was performed using 2,2′-azobis(isobutyronitrile) as an initiator in benzene at 60 °C to prepare poly(methyl methacrylate)-graft-poly(n-hexyl isocyanate) (PMMA-graft-PHIC) graft copolymers. The monomer reactivity ratios of MMA (M₁) and PHIC-MA (M₂) were evaluated as r₁=11.5 and r₂=∼0, exhibiting remarkably lower reactivity of PHIC-MA macromonomer than that of common macromonomers. The resultant graft copolymers were characterized using gel permeation chromatography equipped with low-angle laser light-scattering to determine the molecular weights, and equipped with a refractive index detector and an ultraviolet light detector to estimate a PHIC weight fraction of PMMA-graft-PHIC at the ith elution volume of the GPC chromatogram. There are 2-3 PHIC grafts per PMMA molecule, and the PHIC rodlike chains might be difficult to introduce into the PMMA main chains having higher molecular weights. A specific dimension of PMMA-graft-PHIC in solution was discussed in detail.     

Preparation and characterization of poly(methyl methacrylate)‐intercalated graphite oxide/poly(methyl methacrylate) nanocomposite

A poly(methyl methacrylate)‐intercalated graphite oxide/poly(methyl methacrylate) nanocomposite was prepared by emulsion polymerization of methyl methacrylate in the presence of graphite oxide (GO). GO was synthesized by the oxidization of natural graphite powder with KMnO₄ in concentrated sulfuric acid. The functional groups and microstructure of the oxidized graphite and the composite were carefully characterized by use of X‐ray diffraction, infrared, transmission electron microscopy, and elemental analysis. The electrical conductivity and mechanical properties were also measured. Polym. Eng. Sci. 44:2335–2339, 2004. © 2004 Society of Plastics Engineers.     

Photo-induced graft copolymerization of methyl methacrylate on poly(vinyl alcohol)

Photo-induced graft copolymerization of methyl methacrylate on poly(vinyl alcohol) (PVA) was examined in aqueous solutions. In unoxidized samples, only a few percent of PVA used took part in the formation of grafts, and the percent grafting was very low. However, if Fe²⁺, Fe³⁺, anthraquinone-2,7-disulfonate, or oxalic acid was used as sensitizer, the percent grafting was somewhat improved. Among them, the effect of Fe³⁺ was most remarkable. Oxidized PVA showed a higher initiating activity and was more susceptible to the sensitizing action of Fe³⁺ than unoxidized PVA. As Fe³⁺ has an ability to accelerate the photo-induced scission reaction of PVA chains for both oxidized and unoxidized PVA, it is thought to be very probable that the copolymer formed in the photo-induced systems has a block polymer-type structure like that in systems initiated by ceric ion or hydrogen peroxide.     

Phase behavior of aqueous systems containing block copolymers of poly(ethylene oxide) and poly(propylene oxide)

Phase behavior of aqueous systems containing block copolymers of poly(ethylene oxide (PEO) and poly(propylene oxide) (PPO) was evaluated by building up temperature-concentration phase diagrams. We have studied bifunctional triblock copolymers (HO-PEO-PPO-PEO-OH) and monofunctional diblock copolymers (R-PEO-PPO-OH and R-PPO-PEO-OH, where R length is linear C₄ and C_12–14). The cloud points of the polymer solutions depended on EO/PO ratio, polarity, R length and position of the hydrophilic and hydrophobic segments along the molecule. Such factors influence on the solutions behavior was also analyzed in terms of critical micelle concentration (CMC), which was obtained from surface tension vs. concentration plots. Salts (NaCl and KCl) added into the polymer solutions change the solvent polarity decreasing the cloud points. On the other hand, the cloud points of the polymer solutions increased as a hydrotrope (sodium p-toluenesulfonate) was added. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 1767–1772, 1997