Graphitic nanofillers in PMMA nanocomposites—An investigation of particle size and dispersion and their influence on nanocomposite properties

Mechanical, thermal, and electrical properties of graphite/PMMA composites have been evaluated as functions of particle size and dispersion of the graphitic nanofiller components via the use of three different graphitic nanofillers: “as received graphite” (ARG), “expanded graphite,” (EG) and “graphite nanoplatelets” (GNPs) EG, a graphitic materials with much lower density than ARG, was prepared from ARG flakes via an acid intercalation and thermal expansion. Subsequent sonication of EG in a liquid yielded GNPs as thin stacks of graphitic platelets with thicknesses of ～10 nm. Solution‐based processing was used to prepare PMMA composites with these three fillers. Dynamic mechanical analysis, thermal analysis, and electrical impedance measurements were carried out on the resulting composites, demonstrating that reduced particle size, high surface area, and increased surface roughness can significantly alter the graphite/polymer interface and enhance the mechanical, thermal, and electrical properties of the polymer matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2097–2112, 2007     

Synthesis and characterization of polystyrene‐graphite nanocomposites via surface RAFT‐mediated miniemulsion polymerization

Graphite oxide (GO) was prepared and immobilized with dodecyl isobutyric acid trithiocarbonate (DIBTC) reversible addition‐fragmentation chain transfer (RAFT) agent. The hydroxyl groups of GO were attached to the DIBTC RAFT agent through an esterification process. The resultant modified GO was used for the preparation of polystyrene (PS)/graphite nanocomposites in miniemulsion polymerization. The RAFT‐grafted GO (GO‐DIBTC) at various loadings was dispersed in styrene monomer, and the resultant mixtures were sonicated in the presence of a surfactant (sodium dodecylbenzene sulfonate) and a hydrophobe (hexadecane) to form miniemulsions. The stable miniemulsions thus obtained were polymerized using azobisisobutyronitrile as the initiator to yield encapsulated PS‐GO nanocomposites. The molar mass and polydispersity index of PS in the nanocomposites depended on the amount of RAFT‐grafted GO in the system, in accordance with the features of the RAFT polymerization method. The PS‐GO nanocomposites were of exfoliated morphology, as confirmed by X‐ray diffraction and transmission electron microscopy measurements. The thermal stability and mechanical properties of the PS‐GO nanocomposites were better than those of the neat PS polymer. Furthermore, the mechanical properties were dependent on the modified GO content (i.e., the amount of RAFT‐grafted GO). © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Crystallization behavior of poly(ε‐caprolactone)/multiwalled carbon nanotube composites

Differential scanning calorimetry (DSC), polarized optical microscopy, and X‐ray diffraction methods were used to investigate the isothermal crystallization behavior and crystalline structure of poly(?‐caprolactone) (PCL)/multiwalled carbon nanotube (MWNT) composites. PCL/MWNT composites were prepared via the mixing of a PCL polymer solution with carboxylic groups containing multiwalled carbon nanotubes (c‐MWNTs). Both Raman and Fourier transform infrared spectra indicated that carboxylic acid groups formed at both ends and on the sidewalls of the MWNTs. A transmission electron microscopy micrograph showed that c‐MWNTs were well separated and uniformly distributed in the PCL matrix. DSC isothermal results revealed that introducing c‐MWNTs into the PCL structure caused strongly heterogeneous nucleation induced by a change in the crystal growth process. The activation energy of PCL drastically decreased with the presence of 0.25 wt % c‐MWNT in PCL/c‐MWNT composites and then increased with increasing MWNT content. The result indicated that the addition of c‐MWNT to PCL induced heterogeneous nucleation (lower total activation energy) at a lower c‐MWNT content and then reduced the transportation ability of polymer chains during crystallization processes at a higher MWNT content (higher total activation energy). A correlation between the crystallization kinetics, melting behavior, and crystalline structure of PCL/c‐MWNT composites was also discussed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 598–606, 2006     

Composites of poly(ε‐caprolactone) and Mo6S3I6 Nanowires

Composites of poly(ε‐caprolactone) (PCL) and molybdenum sulfur iodine (MoSI) nanowires were prepared using twin‐screw extrusion. Extensive microscopic examination of the composites revealed the nanowires were well dispersed in the PCL matrix, although bundles of Mo₆S₃I₆ ropes were evident at higher loadings. Secondary electron imaging (SEI) showed the nanowires had formed an extensive network throughout the PCL matrix, resulting in increased electrical conductivity of PCL, by eight orders of magnitude, and an electrical percolation threshold of 6.5 × 10^?3 vol%. Thermal analysis (DSC), WAXD, and hot stage polarized optical microscopy (HSPOM) experiments revealed Mo₆S₃I₆ addition altered PCL crystallization kinetics, nucleation density, and crystalline content. A greater number of smaller spherulites were formed via heterogeneous nucleation. The onset of thermal decomposition (TGA) of PCL decreased by 70°C, a consequence of the thermal degradation of Mo₆S₃I₆ to MoO₃, which in turn accelerates the formation of volatile gases during the first stage of PCL decomposition. Copyright © 2010 John Wiley & Sons, Ltd.     

Polylactide/exfoliated graphite nanocomposites with enhanced thermal stability,mechanical modulus,and electrical conductivity

We have prepared a series of polylactide/exfoliated graphite (PLA/EG) nanocomposites by melt‐compounding and investigated their morphology, structures, thermal stability, mechanical, and electrical properties. For PLA/EG nanocomposites, EG was prepared by the acid treatment and following rapid thermal expansion of micron‐sized crystalline natural graphite (NG), and it was characterized to be composed of disordered graphite nanoplatelets. It was revealed that graphite nanoplatelets of PLA/EG nanocomposites were dispersed homogeneously in the PLA matrix without forming the crystalline aggregates, unlike PLA/NG composites. Thermal degradation temperatures of PLA/EG nanocomposites increased substantially with the increment of EG content up to ～3 wt %, whereas those of PLA/NG composites remained constant regardless of the NG content. For instance, thermal degradation temperature of PLA/EG nanocomposite with only 0.5 wt % EG was improved by ～10 K over PLA homopolymer. Young's moduli of PLA/EG nanocomposites increased noticeably with the increment of EG content up to ～3 wt %, compared with PLA/NG composites. The percolation threshold for electrical conduction of PLA/EG nanocomposites was found to be at 3–5 wt % EG, which is far lower graphite content than that (10–15 wt % NG) of PLA/NG composites. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 850–858, 2010     

A new process of fabricating electrically conducting nylon 6/graphite nanocomposites via intercalation polymerization

A new process was developed to fabricate electrically conducting nylon 6/graphite nanocomposites via intercalation polymerization of ϵ‐caprolactam in the presence of expanded graphite. The transition from an electrical insulator to an electrical semiconductor for nylon 6 occurred when the graphite volume content was 0.75, which was much lower than that of conventional conducting polymer composites. The electrical conductivity reached 10⁻⁴ S/cm when the graphite content was 2.0 vol %. The TEM microphotographs suggested that the low percolation threshold and the great improvement of electrical conductivity could be attributed to the high aspect ratio (width‐to‐thickness), the high expansion ratio in c axis of the graphite sheets and the homogeneous dispersion of the nanoscale graphite particles in the nylon 6 matrix. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1626–1633, 2000     

Influence of graphene oxide incorporation and chemical cross‐linking on structure and mechanical properties of layer‐by‐layer assembled poly(Vinyl alcohol)‐Laponite free‐standing films

Functional fillers in multilayered films provide opportunity in tailoring the mechanical properties through chemical cross‐linking. In this study, Laponite‐graphene oxide co‐dispersion was used to incorporate graphene oxide (GO) easily into polyvinyl alcohol (PVA)/Laponite layer‐by‐layer (LBL) films. The LBL films were found to be uniform and the layer thickness increased linearly with number of depositions. The process was extended to a large number of depositions to investigate the macroscopic mechanical properties of the free‐standing films. The LBL films showed remarkable improvements in mechanical properties as compared to neat PVA film. The GO‐incorporated LBL films displayed higher enhancements in the tensile strength, ductility, and toughness as compared to that of PVA/Laponite LBL films, upon chemical cross‐linking. This suggests the advantageous effects of GO incorporation. Interestingly, cross‐linking of LBL films for longer time period (>1 h) and higher temperature (～80 °C) was not found to be much beneficial. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2377–2387     

Mechanical properties and degradation studies of poly(D,L‐lactide‐co‐glycolide) 50:50/graphene oxide nanocomposite films

Poly(D,L‐lactide‐co‐glycolide) 50:50 (PLGA)/graphene oxide (GO) nanocomposite films were prepared with various GO weight fractions. A significant enhancement of mechanical properties of the PLGA/GO nanocomposite films was obtained with GO weight fractions. The incorporation of only 5 wt% of GO resulted in an ~2.5‐fold and ~4.7‐fold increase in the tensile strength and Young's modulus of PLGA, respectively. The thermomechanical behaviors of composite films were investigated by dynamic mechanical analysis. Results indicated that the values of T_g and storage moduli of the PLGA/GO composites were higher than those of the pristine PLGA. The improvement in oxygen barrier properties of composites was presumably attributed to the filler effect of the randomly dispersed GO throughout the PLGA matrix. In this work, we also studied in vitro biodegradation behavior. PLGA/GO composite films were hydrolyzed at 37°C for periods up to 49 days. Because of the presence of GO nanosheets, degradation of composite films took place more slowly with increasing GO amounts. Copyright © 2013 John Wiley & Sons, Ltd.     

A biocompatible composite based on poly(ε‐caprolactone fumarate) and hydroxyapatite

Fabrication of biodegradable composites applicable as hard tissue substitutes consisting of poly(ε‐caprolactone fumarate) (PCLF), methacrylic acid (MAA), and hydroxyapatite (HA) was investigated. PCLF macromers were synthesized by reaction of PCL diol with fumaryl chloride in the presence of propylene oxide and characterized by gel permeation chromatography, FTIR, and ¹H NMR spectroscopy. Composites were fabricated by incorporating HA as inorganic filler in PCLF matrix which followed by thermal curing of the composition using benzoyl peroxide and MAA as a free radical initiator and reactive diluent, respectively. Uniform distribution of the fine ceramic phase in the polymer matrix was elucidated by scanning electron microscopy. The effects of the initial macromer molecular weight and the filler volume fraction on mechanical properties and cytotoxicity of the composites were also examined. Significant enhancement in the mechanical properties was observed upon increasing HA content and/or initial PCLF molecular weight. The biocompatibility of the specimens was also improved with increasing ceramic phase. Copyright © 2010 John Wiley & Sons, Ltd.     

Preparation and characterization of modified graphite oxide/poly(propylene carbonate) composites by solution intercalation

Modified graphite oxide (MGO)/Poly (propylene carbonate) (PPC) composites with excellent thermal and mechanical properties have been prepared via a facile solution intercalation method. An intercalated structure of MGO/PPC composites was confirmed by X-ray diffraction and scanning electron microscope. The thermal and mechanical properties of MGO/PPC composites were investigated by thermal gravimetric analysis, differential scanning calorimetric, dynamic mechanical analysis, and electronic tensile tester. Due to the nanometer-sized dispersion of layered graphite in PPC matrix and the strong interfacial interaction between MGO and PPC, the prepared MGO/PPC composites exhibit improved thermal and mechanical properties in comparison with pure PPC. Compared with pure PPC, the MGO/PPC composites show the highest thermal stability and the T_g is 13.8 °C higher than that of pure PPC, while the tensile strength (29.51 MPa) shows about 2 times higher than that of pure PPC when only 3.0 wt.% MGO is incorporated. These results indicate that this approach is an efficient method to improve the properties of PPC.     

In situ polymerization and characterization of graphene oxide‐co‐poly(phenylene benzobisoxazole) copolymer fibers derived from composite inner salts

A facile and efficient strategy for preparing well dispersed graphene oxide (GO)‐co‐Poly(phenylene benzobisoxazole) (PBO) copolymer fibers was carried out by direct in situ polycondensation of composite inner salts. The composite inner salts were achieved to improve the dispersivity, solubility, reactivity, and interfacial adhesion of GO in PBO polymer matrix. The structure and morphology of GO‐co‐PBO copolymer fibers have been characterized. It was demonstrated that GO were covalently incorporated with PBO molecular chains and dispersed considerably well in PBO fiber even the GO reach to 3 wt %. Meanwhile, the tensile modulus, tensile strength and thermal stability of GO‐co‐PBO copolymer fibers increased considerably with GO. The mechanism and theoretical calculation of GO enhanced PBO fiber were also discussed. The main reasons for the improvement on performance of PBO fiber should be attributed to good dispersion GO in PBO matrix and covalent bonding networks at the interface between GO and PBO molecular chains. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Rheological behavior of biocomposites of silk fibroin fiber and poly(ε‐caprolactone): Effect of fiber network

Rheological behavior was examined for biocomposites of rod‐like silk fibroin (SF) fiber and poly(ε‐caprolactone) (PCL) to investigate an effect(s) of the SF fiber network therein on the mechanical properties. At 160 °C where PCL was a homogeneous melt, linear viscoelastic tests revealed that the SF/PCL composites hardly relax to behave essentially as elastic solids (more precisely, plastic solids before yielding) at low frequencies. The corresponding equilibrium modulus G₀ increased strongly with the SF volume fraction ?_SF (G₀ ～ ?) and was attributable to the elastic bending of the SF fibers incorporated in the network. The Doi‐Kuzuu model for non‐Brownian rods was modified for the SF/PCL composites by incorporating the rod–rod contact at equilibrium. The G₀ calculated from this model was satisfactorily close to the data, in both ?_SF dependence and magnitude, lending support to the assignment of the composite elasticity to the fiber bending. The storage modulus G′ measured under large‐amplitude oscillatory shear (LAOS) was smaller than the linear viscoelastic G′, and this difference between the linear and nonlinear moduli was enhanced for the composites with a larger SF content and at lower frequencies. This nonlinear effect was attributable to a decrease of the effective fiber–fiber contacts sustaining the elasticity under LAOS. Under steady shear, the SF/PCL composites exhibited nonlinear (plastic) flow behavior associated with the stress overshoot, and their apparent viscosity was comparable to/lower than the viscosity of neat PCL matrix. The overshoot became much less significant on application of a second shear immediately after the first shear, while the overshoot was partly recovered after a quiescent rest between the first and second shears. These nonlinear features were attributable to slippage between shear‐oriented fibers and PCL matrix. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1957–1970, 2009     

Volume‐exclusion effects in polyethylene blends filled with carbon black,graphite, or carbon fiber

Conductive polymer composites possessing a low percolation‐threshold concentration as a result of double percolation of a conductive filler and its host phase in an immiscible polymer blend afford a desirable alternative to conventional composites. In this work, blends of high‐density polyethylene (HDPE) and ultrahigh molecular weight polyethylene (UHMWPE) were used to produce ternary composites containing either carbon black (CB), graphite (G), or carbon fiber (CF). Blend composition had a synergistic effect on electrical conductivity, with pronounced conductivity maxima observed at about 70–80 wt % UHMWPE in the CB and G composites. A much broader maximum occurred at about 25 wt % UHMWPE in composites prepared with CF. Optical and electron microscopies were used to ascertain the extent to which the polymers, and hence filler particles, are segregated. Differential scanning calorimetry of the composites confirmed that the constituent polymers are indistinguishable in terms of their thermal signatures and virtually unaffected by the presence of any of the fillers examined here. Dynamic mechanical analysis revealed that CF imparts the greatest stiffness and thermal stability to the composites. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1013–1023, 2002     

Thermal,mechanical, and topographical evaluation of nonstoichiometric α-cyclodextrin/poly(ε-caprolactone) pseudorotaxane nucleated poly(ε-caprolactone) composite films

Three pseudorotaxanes (PpR) comprised of poly (ε-caprolactone) (PCL) and α-cyclodextrin (α-CD) with varying stoichiometric ratios were synthesized and characterized. Wide-angle X-ray diffraction (WAXD) and thermogravimetric (TGA) analyses provided conclusive evidence for complexation between the guest PCL and host α-CD. The as-synthesized and characterized PpRs were used at 10 and 20% concentrations as nucleants to promote the bulk PCL crystallization in composite films. Both WAXD and TGA provided evidence for intact PpR structures in the composite films. Isothermal differential scanning calorimetric (I-DSC) analyses, performed at various crystallization temperatures demonstrated significant differences in the crystallization patterns among the composite films. In addition, I-DSC analyses showed higher Avrami constant values (n) in the PpR-nucleated composite PCL films (n ~ 3), indicating 3-dimensional crystal growth. In the case of neat PCL films, however, lower n values indicated crystal growth in 1-dimensions or 2-dimensions. Moreover, atomic force microscopic analyses showed large crests and pits in PpR-nucleated PCL composites, with irregular morphologies leading to higher surface roughness. To the contrary, the crests and pits were much smaller in the neat PCL films, resulting in lower surface roughness values. Finally, mechanical testing revealed higher tensile strength for PpR-nucleated PCL composites films, demonstrating larger load bearing capabilities. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1529–1537     

Morphological change of poly (ε‐caprolactone) with a wide range of molecular weight via formation of inclusion complex with α‐cyclodextrin

The effect of molecular weight of poly(ε‐caprolactone) (PCL) on the formation and stability of inclusion complexes (ICs) between α‐cyclodextrin (α‐CD) and PCL was investigated by FTIR, WAXD, and DSC measurements. ICs between α‐CD and PCLs with a wide range of number‐average molecular weight, M_n = 1.21 × 10⁴ – 1.79 × 10⁵, were prepared by mixing the aqueous solution of CD and acetone solution of PCL followed by stirring at 60 °C for 1h and at the room temperature for 1 day. FTIR, WAXD, and DSC measurement showed the PCL chains were included into the α‐CD cavity, and the crystallization of PCL was suppressed in the α‐CD cavity. Stoichiometry and yield of each IC varied with the molecular weight of guest PCL, and the effect of IC formation on the crystallization behaviour of guest polymer decreased with the increase of molecular weight of guest polymer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1433–1440, 2005     

Barrier and Mechanical Properties of Poly(caprolactone)/organoclay Nanocomposites

In this study, biodegradable poly(caprolactone) (PCL) hybrids with two types of organoclays: Cloisite 30B (30B) and Cloisite 93A (93A) have been prepared by melt mixing and their barrier performance to air permeation and mechanical properties were investigated. The hybrids of PCL/30B were found to be nanocomposites resulted from the strong interaction between organic modifier of 30B and PCL and those of PCL/93A were microcomposites. The barrier performance of PCL/30B nanocomposite film to air permeation was much more improved than pure PCL and PCL/93A microcomposites at low organoclay concentration. With the increase of organoclay content the permeability coefficient was also increased that could attributed to the extra tortuous pathway for gas permeation caused by organoclay exfoliation. The barrier behaviour of PCL/30B nanocomposites could be approximately described by a theoretical model developed for composites. The mechanical properties measurements showed that the reinforcement of organoclay 30B in nanocomposites is more significant than 93A in microcomposites. Both tensile modulus and tensile strength were increased in PCL/30B nanocomposites even at at low amount of organoclay without much loss of strain at break as compared to pure PCL. The significant improvements in both barrier and mechanical properties in PCL nanocomposites could be attributed to the fine dispersion state of organoclay 30B platelets in PCL matrix and the strong interaction between organic modifier of 30B and matrix molecules.     

Improved polyvinylpyrrolidone (PVP)/graphite nanocomposites by solution compounding and spray drying

In order to evaluate the roles of graphite dispersion on the functional properties of the composites, PVP/graphite nanocomposites were prepared by blending the aqueous suspension of expanded graphite sheets and polyvinylpyrrolidone (PVP) aqueous solution by ultrasonic treatment, followed by spray drying and direct drying as a comparison individually. The effects of graphite loading and drying method on the dispersion of graphite and the resultant properties of the composites such as electrical and thermal conductivity, friction, and dynamic mechanical properties were studied. The results from transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X‐ray diffraction showed that the composites prepared by fast spray drying exhibited a higher degree of exfoliation and a better dispersion of graphite sheets in the PVP matrix than the corresponding composites prepared by direct drying, leading to a conclusion that fast spray drying can effectively prevent from re‐stacking of the exfoliated graphite sheets as illustrated. As a result, dynamic mechanical thermal analysis showed significant increases in the storage modulus and glass transition temperature for the composites prepared by spray drying. Besides, the spray drying as well greatly improved the electrical and thermal conductivity of the composites. It was also found that the electrical and thermal conductivity of the composites strongly depended on the graphite dispersion, while the friction coefficient unexpectedly does not. Increasing graphite loading level might enhance the probability of graphite sheets re‐stacking, resulting in poor graphite dispersion. Copyright © 2011 John Wiley & Sons, Ltd.     

A novel shape memory poly(ε‐caprolactone) network via UV‐triggered thiol‐ene reaction

A facile method to prepare shape memory polymers crosslinked by SiO₂ is described. A series of biodegradable shape memory networks were obtained through thiol‐ene reaction triggered by UV irradiation between surface‐thiol‐modified SiO₂ nanoparticles and end‐acrylate poly (ε‐caprolactone) (PCL). The highly selective thiol‐ene reaction ensured a uniform distribution of PCL chains between crosslinkers, contributing well‐defined network architecture with enhanced mechanical and shape‐memory properties. Thiol‐functionalized silica nanoparticle was characterized by using FTIR and XPS analysis, and ¹H NMR spectra was used to confirm the successful modification of terminal hydroxyl group of PCL diol. Surface‐modified silica particles were found well dispersible in acrylate‐capped PCL supported by SEM. Thermal and crystalline behaviors of the obtained polymers were analyzed by DSC and XRD, and DMA measurement proved good mechanical property. The shape memory behavior and tensile strength was somewhat tunable by the length of PCL. Acceptably, sample SiO₂‐SMP2k presented 99% recovery ratio and 97% shape fixity, and its relatively high tensile strength showed an attractive potential for biomedical application. Finally, a possible molecular mechanism accounting for the shape memory property was illustrated. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 692–701     

Straightforward synthesis of conductive graphene/polymer nanocomposites from graphite oxide

The reduction of graphite oxide (GO) in the presence of reactive poly(methyl methacrylate) (PMMA), under mild biphasic conditions, directly affords graphene grafted with PMMA. The resulting nanocomposite shows excellent electrical conductivities resulting from the optimal dispersion and exfoliation of graphene in the polymer matrix.     

Tailor‐made hybrid nanostructure of poly(ethyl acrylate)/clay by surface‐initiated atom transfer radical polymerization

Hybrid nanoarchitecture of tailor‐made Poly(ethyl acrylate)/clay was prepared by surface‐initiated atom transfer radical polymerization (SI‐ATRP), by tethering ATRP initiator on active hydroxyl group, present in surface as well as in the organic modifier of the clay used. Extensive exfoliation was facilitated by using these initiator modified clay platelets. Poly(ethyl acrylate) chains with controlled polymerization and narrow polydispersities were forced to be grown from within the clay gallery (intergallery) as well as from the outer surface (extragallery) of the clay platelets. The polymer chains attached onto clay surfaces might have the potential to provide the composites with enhanced compatibility in blends with common polymers. Attachment of the initiator on clay platelets was confirmed by Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), elemental analysis, Wide‐angle X‐ray diffraction (WAXD), and microscopic analysis. Finally, end group analysis (by Matrix‐Assisted Laser Desorption Ionization Mass Spectrometry, and chain extension experiment) of the cleaved polymer and morphological study (by WAXD, Transmission Electron Microscopy), performed on the polymer grafted clays examined the effect of grafting on the efficiency of polymerization and the degree of dispersion of clay tactoids in polymer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5014–5027, 2008