Compatibilization of blends of polybutadiene and poly(methyl methacrylate) with poly(butadiene-block-methyl methacrylate)

Compatibilization of blends of polybutadiene and poly(methyl methacrylate) with butadiene-methyl methacrylate diblock copolymers has been investigated by transmission electron microscopy. When the diblock copolymers are added to the blends, the size of PB particles decreases and their size distribution gets narrower. In PB/PMMA7.6K blends with P(B-b-MMA)25.2K as a compatibilizer, most of micelles exist in the PMMA phase. However, using P(B-b-MMA)38K as a compatibilizer, the micellar aggregation exists in PB particles besides that existing in the PMMA phase. The core of a micelle in the PMMA phase is about 10 nm. In this article the influences of temperature and homo-PMMA molecular weight on compatibilization were also examined. At a high temperature PB particles in blends tend to agglomerate into bigger particles. When the molecular weight of PMMA is close to that of the corresponding block of the copolymer, the best compatibilization result would be achieved. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36 : 85–93, 1998     

Novel blends from agave fibers and poly(methyl methacrylate)

Cellulose-rich fibers were isolated from Agave lechuguilla (AL) and Agave fourcroydes (AF) growing in the Mexican northeast. These fibers are a valuable feedstock for the preparation of blends with synthetic polymers like poly(methyl methacrylate), PMMA. Blends of different types of agave fibers (dewaxed, mercerized, and grafted) and PMMA were prepared and investigated by means of tension measurements and dynamic mechanical analysis. The fiber-containing blends are more stable than the plain PMMA. Surprisingly, the mechanical stability of the blends is practically independent of the pretreatment of the fibers. Methyl methacrylate (MMA) was grafted onto the biopolymer fibers initiated by the cerammonium nitrate redox initiator. Grafting yields of 26.5% were realized with fibers from AL while up to 75.8% MMA was grafted onto fibers from AF. The materials were characterized by means of FTIR spectroscopy and DSC.     

Thermal oxidation of blends of poly(ethylene oxide) and poly(methyl methacrylate)

Thermal oxidation of poly(ethylene oxide) (PEO) and its blends with poly(methyl methacrylate) (PMMA) were studied using oxygen uptake measurements. The rates of oxidation and maximum oxygen uptake contents were reduced as the content of PMMA was increased in the blends. The results were indicative of a stabilizing effect by PMMA on the oxidation of PEO. The oxidation reaction at 140°C was stopped at various stages and PMMA was separated from PEO and its molecular weights were measured by gel permeation chromatography (GPC). The decrease in the number-average molecular weight of PMMA was larger as the content of PEO increased in the blends. The visual appearance of the films suggested that phase separation did not occur after thermal oxidation. The activation energy for the rates of oxidation in the blends was slightly increased compared to pure PEO. © 1992 John Wiley & Sons, Inc.     

Thermogravimetric studies on poly(methyl methacrylate), poly(tetrahydrofuran) and their blends

TG studies are given for PMMA prepared by radical polymerization, PTHF prepared by cationic polymerization, and their blends. A procedure is proposed for determining the activation energy, frequency factor, and the order of events corresponding to the respective stages of the multistage TG curves. The order of the initial event of PMMA is not the 1st. It is shown for this discussion that the relationship between mass loss and time of the 2nd order reaction is similar to that of the depolymerization including the vaporization process at the earlier times. Some of TG curves of PTHF are not dependent on the heating rate. This independence depends on the size of sample. The order of event of PTHF, which is obtained from TG curves dependent on the heating rate, is the 0th. The event order equal to the 0th reflects major contribution of vaporization in the event. The TG behaviors shown by the procedure mentioned above for the PMMA/PTHF blends with the smaller PMMA or PTHF contents cancel those of PMMA or PTHF. This revised version was published online in July 2006 with corrections to the Cover Date.     

Morphological studies of poly(vinylidene fluoride) and its blends with poly(methyl methacrylate)

Both pure poly(vinylidene fluoride) (PVF₂) and its blends with poly(methyl methacrylate) (PMMA) develop a variety of morphologies when they are crystallized above the 420–424 K range. Two populations of spherulites as well as axialitelike growths are observed. Addition of the PMMA lowers the temperature where these new morphologies develop, makes the spherulites more open, causes the banding periodicity to decrease, and increases the number of small, coarse spherulites. These structures melt in three regimes. The highest-melting-point crystals arise only from a solid-solid transformation of the lowest-melting-point ones. This solid-state transition sometimes causes mixed spherulites to be formed in the blends. Electron and wide-angle x-ray diffraction show the lowest-melting-point species to be α crystals, while the other two are γ crystals. The highest-melting-point species, labeled γ′, and the α crystals seem to be more ordered than the other γ crystals.     

Melting studies of poly(vinylidene fluoride) and its blends with poly(methyl methacrylate)

Blends of poly(vinylidene fluoride) (PVF₂) and poly(methyl methacrylate) exhibit complex melting behavior when crystallized at low undercoolings. Three crystals comprised of two different PVF₂ forms grow. Hoffman-Weeks plots of the observed melting points T_m of these crystals versus crystallization temperatures are constructed. The lowest-melting-point species, the α form, shows a change in slope which is attributed to fewer head-to-head PVF₂ units trapped in the crystal at higher temperatures. Defect energies in the crystal due to these units are calculated to be from 6.3 to 10.3 kJ/mol. Estimating lamellar thicknesses from the slopes of the two regions gives much more reasonable values when the high-temperature data are used. Removal of kinetic effects that lower the observed T_m by extrapolating the data to obtain T permits the thermodynamic interaction energy density B between the two polymers to be obtained. The low-temperature α-form data give B = ?8.83 × 10⁶ J/m³. The high-temperature α-form data and the T of the γ-form crystals both show B to vary from ?5.40 × 10⁶ to ?2.96 × 10⁷ J/m³ as the blend composition goes from 40.1 vol % to pure PVF₂.     

Compatibility in poly(ethylene oxide)–poly(methyl methacrylate) blends

The compatibility of poly(ethylene oxide)-poly(methyl methacrylate) (PEO-PMMA) blends were examined covering the complete composition range. Up to 20% of PEO content films were transparent and glass transition temperatures were determined by DSC and by refractive index vs. temperature measurements. Only one T_g was obtained for these samples and the relationship between T_g and composition has been evaluated. At higher PEO content crystallization took place and the films were opaque. Melting temperatuures of PEO in blends were determined by DSC. Melting point depression was observed for increasing proportion of PMMA and the binary interaction parameter has been calculated.     

Robust isocratic liquid chromatographic separation of functional poly(methyl methacrylate)

The separation of telechelic poly(methyl methacrylate) (PMMA) prepolymers based on the number of end-groups under critical liquid chromatography (LC) conditions has been studied using a bare-silica column, which can interact with polar functional groups. The critical solvent compositions for non-functional, mono-functional and bi-functional PMMAs were determined in normal-phase LC using mixtures of acetonitrile and dichloromethane (DCM) of varying composition as the mobile phase. The telechelic prepolymers were successfully separated according to hydroxyl (OH) functionality (with zero, one, or two OH groups, respectively) under the critical conditions, in which fast (5 min), base-line separations were obtained independent of molecular weight. Changing the column temperature, flow rate, and mobile-phase composition within a certain range did not affect the functionality separation. Therefore this isocratic LC separation method is quite robust. Evaporative light-scattering detector (ELSD) calibration curves were used for the quantitative analysis of functional PMMA prepolymers.     

Thermal degradation studies in poly(vinyl chloride)/poly(methyl methacrylate) blends

The miscibility, morphology, and thermal properties of poly(vinyl chloride) (PVC) blends with different concentrations of poly(methyl methacylate) (PMMA) have been studied. The interaction between the phases was studied by FTIR and by measuring the glass transition temperature (T_g) of the blends using differential scanning calorimetry. Distribution of the phases at different compositions was studied through scanning electron microscopy. The FTIR and SEM results show little interaction and gross phase separation. The thermogravimetric studies on these blends were carried out under inert atmosphere from ambient to 800 °C at different heating rates varying from 2.5 to 20 °C/min. The thermal decomposition temperatures of the first and second stage of degradation in PVC in the presence of PMMA were higher than the pure. The stabilization effect on PVC was found most significant with 10 wt% PMMA content in the PVC matrix. These results agree with the isothermal degradation studies using dehydrochlorination and UV-vis spectroscopic results carried out on these blends. Using multiple heating rate kinetics the activation energies of the degradation process in PVC and its blends have been reported.     

Phase separation studies on poly(vinylidene fluoride) and poly(methyl methacrylate) quenched blends

A combined study by SAXS and DSC on quenched blends of PVDF and PMMA is presented. Attention is focused on the first stage of the phase separation process during annealing that is shown to be mainly determined by the diffusion of the PVDF molecules from the amorphous blend phase towards the crystals growth front. The experimental monomer diffusion constants at T > T_g are compared with those expected theoretically using the approximation of the fast model process and the WLF equation for the relaxation frequency of the monomer. The nature and composition of the crystal interphase are discussed in terms of the SAXS invariant for the whole system and the calorimetric data derived from the T_g transitions observed.     

Miscibility and crystallization behavior in blends of poly(methyl methacrylate) and poly(vinylidene fluoride): Effect of star‐like topology of poly(methyl methacrylate) chain

A tetraarmed star‐shaped poly(methyl methacrylate) (s‐PMMA) was synthesized via atom transfer radical polymerization with 2‐bromoisobutyryl pentaerythritol as the initiator. For comparison, a linear PMMA with the identical molecular weight (l‐PMMA) was also prepared. The blends of the two PMMA samples with poly (vinylidene fluoride) (PVDF) were prepared to investigate the effect of macromolecular topological structure on miscibility and crystallization behavior of the binary blends. The behavior of single and composition‐dependent glass transition temperatures was found for the blends of s‐PMMA with PVDF, indicating that the s‐PMMA is miscible with PVDF in the amorphous state just like l‐PMMA. The miscibility was further evidenced by the depression of equilibrium melting points. It is found that the blends of s‐PMMA and PVDF displayed the larger k value of Gordon–Taylor equation than the blends of l‐PMMA and PVDF blends. According to the depression of equilibrium melting points, the intermolecular parameters for the two blends were estimated. It is noted that the s‐PMMA/PVDF blends displayed the lower interaction parameter than l‐PMMA/PVDF blends. The isothermal crystallization kinetics shows that the crystallization of PVDF in the blends containing s‐PMMA is faster than that in the blends containing the linear PMMA. The surface‐folding free energy of PVDF chains in the blends containing s‐PMMA is significantly lower than those in the blends containing l‐PMMA. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2580–2593, 2007     

Uniaxial drawing of poly(ethyleneoxide)/poly(methyl methacrylate) blends by solid-state extrusion

Ultradrawn ribbons of solution-cast blends of poly(ethylene oxide) (PEO)/poly(methyl methacrylate) (PMMA) have been prepared by a solid-state coextrusion in a capillary rheometer. An increase of noncrystallizable PMMA in the blends drastically decreased the drawability from a draw ratio of 36 for pure PEO to 5 for a mixture of PEO/PMMA 40/60% by weight. A low crystallinity and depression of melting temperature for PEO were observed with increasing draw. The Flory-Huggins theory for melting temperature depression has been used to derive the binary interaction parameter for these blends.     

The structure and properties of drawn blends of poly (vinylidene fluoride) and poly (methyl methacrylate)

A blend consisting of equal proportions of poly (vinylidene fluoride) and poly (methyl methacrylate) has been prepared and drawn to draw ratios up to 7. The mechanical properties and the structure and morphology of the samples have been measured, the latter using differential scanning calorimetry, optical microscopy, and various x-ray techniques. A structural model is proposed for the drawn materials which accounts for the mechanical properties and for the response of the crystalline regions of the material to an applied stress.     

Thermo-oxidative dehydrochlorination of rigid and plasticised poly(vinyl chloride)/poly(methyl methacrylate) blends

The aim of this work was to study the thermo-oxidative dehydrochlorination of rigid and plasticised poly(vinyl chloride)/poly(methyl methacrylate) blends. For that purpose, blends of variable compositions from 0 to 100 wt% were prepared in the presence (15, 30 and 50 wt%) and in the absence of diethyl-2-hexyl phthalate as plasticiser. Their miscibility was investigated by using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). Their thermo-oxidative degradation at 180 ± 1 °C was studied and the amount of HCl released from PVC was measured by a continuous potentiometric method. Degraded samples were characterised, after purification, by FTIR spectroscopy and UV-visible spectroscopy. The results showed that the two polymers are miscible up to 60 wt% of poly(methyl methacrylate) (PMMA). This miscibility is due to a specific interaction of hydrogen bonding type between carbonyl groups (CO) of PMMA and hydrogen (CHCl) groups of PVC as shown by FTIR analysis. On the other hand, PMMA exerted a stabilizing effect on the thermal degradation of PVC by reducing the zip dehydrochlorination, leading to the formation of shorter polyenes.     

Thermal and photochemical stability of poly(methyl methacrylate) and its blends with poly(vinyl acetate)

An investigation of the thermal stability of poly(methyl methacrylate) (PMMA) blends with poly(vinyl acetate) (PVAc) revealed that PVAc acts as a stabilizer as concerns thermal and photochemical degradation when the processes take place in air. The temperatures of decomposition of these blends are higher than that of pure PMMA. The efficiency of photodegradation and photooxidation in the blends is lower than that of pure PMMA.     

Fracture behavior of amorphous and semicrystalline blends of poly(vinylidene fluoride) and poly(methyl methacrylate)

The fracture behavior of blends of poly(vinylidene fluoride) and poly(methyl methacrylate) was investigated all over the composition range. A detailed analysis of the net stress versus crack opening displacement curves was performed. Fracture surface observations allowed statements on the process zone characteristics ahead of the crack tip. For the amorphous blends, the crack initiation energy is well related to the glass transition temperature. For the semicrystalline blends, the fracture energy is correlated with the degree of crystallinity. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Entanglement between dissimilar chains in compatible polymer blends: poly(methyl methacrylate) and poly(vinylidene fluoride)

The plateau modulus and zero-shear melt viscosity of binary compatible blends of poly(methyl methacrylate) and poly(vinylidene fluoride) were measured by dynamic oscillation and shear creep, and used to analyze the entanglement between dissimilar chains and its effect on melt viscosity. It is found that dissimilar chains are less likely to entangle with each other than similar chains, resulting in a large reduction of zero-shear melt viscosity in this system.     

Homogeneous and multiphase poly(methyl methacrylate) graft polymers via the macromonomer method

Anionic and group transfer polymerization processes were used to synthesize controlled molecular weight methacryloyloxy functionalized poly(dimethylsiloxane) and poly(methyl methacrylate) macromonomers having a narrow molecular weight distribution and high percent functionality. These macromonomers were anionically copolymerized with methyl methacrylate (MMA) to afford poly(methyl methacrylate)-graft-poly(methyl methacrylate) (PMMA-g-PMMA) and poly(methyl methacrylate)-graft-poly(dimethylsiloxane) (PMMA-g-PDMS) polymers having not only narrow molecular weight distribution graft parts but also backbone parts. The PMMA-g-PDMS system was fractionated using supercritical chlorodifluoromethane to determine its chemical composition distribution (CCD). The CCD for the PMMA-g-PDMS copolymerized in a living manner was substantially more narrow than the free radically copolymerized material. The PMMA-g-PMMA system was used to study the dilute solution properties of branched homopolymers. The appropriateness of the universal calibration gel permeation chromatography (GPC) method for branched systems exhibiting long chain branching was reaffirmed.     

Miscibility and crystallization behaviors of stereocomplex-type poly(l- and d-lactide)/poly(methyl methacrylate) blends

Stereocomplex-poly(l- and d-lactide) (sc-PLA) and poly(methyl methacrylate) (PMMA) blends were prepared by solution blending at PMMA loadings from 20 to 80 mass%. The miscibility and crystallization behaviors of the blends have been studied in detail by differential scanning calorimeter. The single-glass transition temperatures (T _g) of the blends demonstrated that the obtained system was miscible in the amorphous state. It was observed that the crystallization peak temperature of sc-PLA/PMMA blends was marginally lower than that of neat sc-PLA at various cooling rates, indicating the dilution effect of PMMA on the sc-PLA component to restrain the overall crystallization process. In the study of isothermal crystallization kinetics, the reciprocal value of crystallization peak time ( \( t_{\text{p}}^{ - 1} \) ) decreased with increasing PMMA content, indicating that the addition of non-crystalline PMMA inhibited the isothermal crystallization of sc-PLA at an identical crystallization temperature (T _c). Moreover, the negative value of Flory–Huggins interaction parameter (χ ₁₂ = ?0.16) of the blend further indicated that sc-PLA and PMMA formed miscible blends.