Hydrogen bonding,mechanical properties,and surface morphology of clay/waterborne polyurethane nanocomposites

A novel clay/waterborne polyurethane (WPU) nanocomposite was synthesized from polyurethane and saponite organoclay. The clay was organically modified with various swelling agents, the effect of which has been investigated. Hydrogen bonding between organic and inorganic materials was characterized with Fourier transform infrared (FTIR) spectroscopy. The results implied that hydrogen bonding increased when organoclay was added. Mechanical and wear property studies revealed that introducing clay into waterborne polyurethane will enhance the Young's modulus (from 56 to 126 MPa), the maximum stress (from 3.9 to 7.6 MPa), and the elongation at break (from 27.7 to 58.7%) of the nanocomposite by a factor of two, whereas the wear loss will be only one third of the neat waterborne polyurethane. Atomic force microscopy (AFM) was used to analyze the surface morphology of the nanocomposite. An AFM microphotograph showed that the surface of the clay/waterborne polyurethane nanocomposite was smoother when clay was added in waterborne polyurethane. The average roughness (R_a) decreased from 1.00 to 0.12. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1–12, 2005     

Polymorphism behavior of poly(ethylene naphthalate)/clay nanocomposites

Thermally stable organically modified clays based on 1,3‐didecyl‐2‐methylimidazolium (IM2C10) and 1‐hexadecyl‐2,3‐dimethyl‐imidazolium (IMC16) were used to prepare poly(ethylene naphthalate) (PEN)/clay nanocomposites via a melt intercalation process. The clay dispersion in the resulting hybrids was studied by a combination of X‐ray diffraction, polarizing optical microscopy, and transmission electron microscopy. It was found that IMC16 provided better compatibility between the PEN matrix and the clay than IM2C10, as evidenced by some intercalation of polymer achieved in the PEN/IMC16‐MMT hybrid. The effects of clay on the crystal structure of PEN were investigated. It was found that both pristine MMT and imidazolium‐treated MMT enhanced the formation of the β‐crystal phase under melt crystallization at 200 °C. At 180 °C, however, the imidazolium‐treated MMT was found to favor the α‐crystal form instead. The difference in clay‐induced polymorphism behavior was attributed to conformational changes experienced by the clay modifiers as the crystallization temperature changes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1040–1049, 2006     

Preparation and properties of poly(vinyl alcohol)–vermiculite nanocomposites

A vermiculite (VMT) dispersion in water was blended with aqueous poly(vinyl alcohol) (PVA). The properties of the PVA–VMT nanocomposites greatly depended on the preparation procedure because of the chemical reactions and physical interactions involved. The samples were prepared in two steps to investigate the properties of the PVA–VMT nanocomposites. The VMT was first pretreated and delaminated with hydrochloric acid. The delaminated VMT was then added to the PVA solution with various mixing times. The structure and properties of the films were investigated. From X‐ray diffraction and transmission electron microscopy, the VMT layers were found to be well dispersed individually in the PVA–VMT blends. The effect of the VMT content on the thermal behavior of the PVA–VMT blends was also studied with differential scanning calorimetry. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 749–755, 2003     

Preparation and characterization of waterborne poly(urethane urea) with well‐defined hard segments

A series of polyester‐based poly(urethane urea) (PUU) aqueous dispersions with well‐defined hard segments were prepared from polyester polyol, 4,4′‐diphenylmethane diisocyanate, dimethylolpropionic acid, 1,4‐butanediol, isophorone diisocyanate, and ethylenediamine. These anionic‐type aqueous dispersions had good dispersity in water and were stable at the ambient temperature for more than 1 year. For these aqueous dispersions, the particle size decreased as the hard‐segment content increased, and the polydispersity index was very narrow (<1.10). Films prepared with the PUU aqueous dispersions exhibited excellent waterproof performance: the amount of water absorption was as low as 5.0 wt %, and the contact angle of water on the surface of this kind of film was as high as 103° (this led to a hydrophobic surface). The water‐resistant property of these waterborne PUU films could be well correlated with some crystallites and ordered structures of the well‐defined hard segments formed by hydrogen bonding between the urethane/urethane groups and urethane/ester groups, as well as the degree of microphase separation between the hard and soft segments in the PUU systems. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2606–2614, 2005     

Hydrogen bonding interaction and crystallization behavior of poly (butylene succinate‐co‐butylene adipate)/thiodiphenol complexes

The poly (butylene succinate‐co‐butylene adipate) (PBSA)/thiodiphenol (TDP) complexes were prepared by melt blending. Intermolecular hydrogen bonding between carbonyl group of PBSA and hydroxyl group of TDP formed as verified by a combination FTIR and peak fitting technique. As a result, the crystallization temperature, melting temperature, crystallinity and crystallization rate of PBSA decreased with addition of TDP, implying impeded crystallization and reduced lamellar thickness. On the basis of Lauritzen–Hoffman analysis, the fold surface energy (σ_e) and work of chain folding (q) were increased by TDP incorporation. POM observation exhibited concentric ring‐banded spherulites for samples with 10 and 20 wt% TDP. A peculiar ring‐banded pattern with discrepant band spacing was obtained for the first time by addition of 30 wt% TDP, whose formation mechanism remains to be discussed. Copyright © 2016 John Wiley & Sons, Ltd.     

Structure and properties of composites compression‐molded from silk fibroin powder and waterborne polyurethane

The degummed silk filament was pulverized with a home‐made machine to obtain the silk fibroin (SF) powder with the diameter of around 3 µm. The resulting SF powder was blended with waterborne polyurethane (WPU) aqueous dispersion, and then was dried and compression‐molded to prepare novel blended materials with improved miscibility and mechanical properties. WPU acted as a plasticizer and one of the components for the blends during the compression‐molded process. The structure, morphology, and properties of the blended films were investigated. The results indicated that β‐sheet of SF existed in the blended films. The SEM images showed that the cross‐section of the blended films exhibited an overall homogeneous morphology. Furthermore, the transmission electron microscope observation exhibited that some sphere‐like SF particles were well dispersed in the WPU matrix. The hydrogen bond interaction between SF and WPU in the blended films led to an increase of the glass transition temperature for the soft segment of WPU in the blended films. The blended films showed an improved Young's modulus and tensile strength from 1.2 to 288.9 MPa and 0.3 to 16.5 MPa, respectively, with the increasing of SF up to a content of 70 wt%. The hydrogen‐bonding interactions existing in SF and WPU and compression molding method played the important role in improving the miscibility and mechanical properties of the blended films. Copyright © 2011 John Wiley & Sons, Ltd.     

Polymer/clay nanocomposites through multiple hydrogen‐bonding interactions

An 2‐ureido‐4[1H]pyrimidinone (UPy) motif with self‐association capability (through quadruple hydrogen bonds) was successfully anchored onto montmorillonite clay layers. Polymer/clay nanocomposites were prepared by specific hydrogen bonding interactions between surface functionalized silica nanoclays and UPy‐bonded supramolecular poly(ethylene glycol) or poly(?‐caprolactone). The mixed morphologies including intercalated layers with a non‐uniform separation and exfoliated single layers isolated from any stack were determined by combined X‐ray diffraction and transmission electron microscopic measurements. Thermal analyses showed that all nanocomposites had higher decomposition temperatures and thermal stabilities compared with neat polymer. The differential scanning calorimetric data implied that the crystallinity of polymers did not show essential changes upon introduction of organomodified UPy clays. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 650–658     

Anion Recognition with Hydrogen‐Bonding Cyclodiphosphazanes

Modular cyclodiphosph(V)azanes are synthesised and their affinity for chloride and actetate anions were compared to those of a bisaryl urea derivative ( 1 ). The diamidocyclodiphosph(V)azanes cis‐[{ArNHP(O)(μ‐tBu)}₂] [Ar=Ph ( 2 ) and Ar=m‐(CF₃)₂Ph ( 3 )] were synthesised by reaction of [{ClP(μ‐NtBu)}₂] ( 4 ) with the respective anilines and subsequent oxidation with H₂O₂. Phosphazanes 2 and 3 were obtained as the cis isomers and were characterised by multinuclear NMR spectroscopy, FTIR spectroscopy, HRMS and single‐crystal X‐ray diffraction. The cyclodiphosphazanes 2 and 3 readily co‐crystallise with donor solvents such as MeOH, EtOH and DMSO through bidentate hydrogen bonding, as shown in the X‐ray analyses. Cyclodiphosphazane 3 showed a remarkably high affinity (log[K]=5.42) for chloride compared with the bisaryl urea derivative 1 (log[K]=4.25). The affinities for acetate (AcO^?) are in the same range ( 3 : log[K]=6.72, 1 : log[K]=6.91). Cyclodiphosphazane 2 , which does not contain CF₃ groups, exhibits weaker binding to chloride (log[K]=3.95) and acetate (log[K]=4.49). DFT computations and X‐ray analyses indicate that a squaramide‐like hydrogen‐bond directionality and C_α?H interactions account for the efficiency of 3 as an anion receptor. The C_α?H groups stabilise the Z,Z‐ 3 conformation, which is necessary for bidentate hydrogen bonding, as well as coordinating with the anion.     

Hydrogen‐Bonded Complexes between 4‐Alkoxystilbazoles and Fluorophenols: Solid‐State Structures and Liquid Crystallinity

48 new hydrogen‐bonded complexes have been prepared by combining 16 fluorophenols of general formula C₆F_nH_5?nOH with three different alkoxystilbazoles (butyloxy‐, octyloxy‐ and dodecyloxy‐). Single‐crystal X‐ray structures were obtained for 10 of the 16 complexes of octyloxystilbazole from which it was found that most of the structures could be collected into one of two groups according to both the motif shown by the complex and by the solid‐state packing. Because all but one crystallised in the P$\bar 1$ space group, meaningful comparisons could be drawn and it was observed that six structures were extremely close in nature so that significant molecular overlap was found. On this basis, doubt is cast on the significance of some of the weaker intermolecular contacts found in the solid state. 40 of the new complexes showed liquid‐crystal properties and it was found that although complexes of butyloxystilbazole were all nematic, almost all of those with dodecyloxystilbazole showed a smectic A (SmA) phase. Complexes of octyloxystilbazole showed a mixture of both. Structure/property correlations showed that clearing points were independent of the pK_a of the phenol. The most stable mesophases were found when the fluorophenol contained a fluorine at the 2‐position, which was interpreted in terms of the formation of an intramolecular H???F hydrogen bond to give a six‐membered ring linking the two components into a stable, coplanar conformation. The least stable mesophases were found when no such ring formation was possible and the phenol was relatively free to move.     

Intercalated poly(vinylidene fluoride)/clay nanocomposites: Structure and properties

The preparation and characterization of melt‐intercalated poly(vinylidene fluoride) (PVDF)/clay nanocomposites are reported. Organophilic clay (clay treated with dimethyl dihydrogenated tallow quaternary ammonium chloride) was used for the nanocomposite preparation. The composites were characterized with X‐ray diffraction (XRD), differential scanning calorimetry (DSC), and dynamic mechanical analysis (DMA). XRD results indicated the intercalation of the polymer in the interlayer spacing. The incorporation of clay in PVDF resulted in the β form of PVDF. DSC nonisothermal curves showed an increase in the melting and crystallization temperatures along with a decrease in crystallinity. Isothermal crystallization studies show an enhanced rate of crystallization with the addition of clay. DMA indicated significant improvements in the storage modulus over a temperature range of ?100 to 150 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 31–38, 2003     

Competitive hydrogen bonding and self‐assembly in poly(2‐vinyl pyridine)‐block‐poly(methyl methacrylate)/poly(hydroxyether of bisphenol A) blends

Blends of poly(2‐vinyl pyridine)‐block‐poly(methyl methacrylate) (P2VP‐b‐PMMA) and poly(hydroxyether of bisphenol A) (phenoxy) were prepared by solvent casting from chloroform solution. The specific interactions, phase behavior and nanostructure morphologies of these blends were investigated by Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), dynamic light scattering (DLS), atomic force microscopy (AFM), and transmission electron microscopy (TEM). In this block copolymer/homopolymer blend system, it is established that competitive hydrogen bonding exists as both blocks of the P2VP‐b‐PMMA are capable of forming intermolecular hydrogen bonds with phenoxy. It was observed that the interaction between phenoxy and P2VP is stronger than that between phenoxy and PMMA. This imbalance in the intermolecular interactions and the repulsions between the two blocks of the diblock copolymer lead to a variety of phase morphologies. At low phenoxy concentration, spherical micelles are observed. As the concentration increases, PMMA begins to interact with phenoxy, leading to the changes of morphology from spherical to wormlike micelles and finally forms a homogenous system. A model is proposed to describe the self‐assembled nanostructures of the P2VP‐b‐PMMA/phenoxy blends, and the competitive hydrogen bonding is responsible for the morphological changes. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1894–1905, 2009     

Thermal properties of poly(lactic acid)/organo-montmorillonite nanocomposites

Poly(lactic acid)/organo-montmorillonite nanocomposites were prepared by melt intercalation technique. Maleic anhydride-grafted ethylene propylene rubber (EPMgMA) was added into the PLA/OMMT in order to improve the compatibility and toughness of the nanocomposites. The samples were prepared by single screw extrusion followed by compression molding. The effect of OMMT and EPMgMA on the thermal properties of PLA was studied. The thermal properties of the PLA/OMMT nanocomposites have been investigated by using differential scanning calorimeter (DSC) and thermo-gravimetry analyzer (TG). The melting temperature (T _m), glass transition temperature (T _g), crystallization temperature (T _c), degree of crystallinity (χ_c), and thermal stability of the PLA/OMMT nanocomposites have been studied. It was found that the thermal properties of PLA were greatly influenced by the addition of OMMT and EPMgMA.     

Wide angle X‐ray diffraction and Fourier transform infrared dichroism studies of stretched‐recovery‐restretched process of polyurethane/clay nanocomposite

An intercalated polyurethane (PU) /clay nanocomposite was prepared by in situ intercalative polymerization. The PU/clay nanocomposite pellet or film samples were stretched‐recovery‐restretched, using selfmade microstretching tools. The changes of the basal spacings of clay and the orientation of polymer chain segments during the stretched‐recovery‐restretched process were studied by wide angle X‐ray diffraction (WAXD) and Fourier transform infrared (FTIR) dichoism techniques. The WAXD results show that the basal spacing of clay did not change obviously, indicating that no macromolecular chains entered or moved out of the interlayer space, and the orientations of both hard and soft segments inside the interlayer space did not change obviously, either. The FTIR dichroism tests suggest that outside the interlayer space, the orientation of the hard chain segment increased, decreased, and then increased again during the stretched‐recovery‐restretched process. However, no obvious changes of the degree of orientation of the soft segment were observed during the processes, the slightly orientation might be released during the relaxation process before the measurements. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 654–660, 2007     

Synthesis and characterization of poly(methylmethacrylate)/silica nanocomposites: Study of the interphase by solid‐state NMR and structure/properties relationships

Organic/inorganic nanocomposites were synthesized from poly(methylmethacrylate) (PMMA) and properly modified silica nanoparticles by in situ polymerization. Methacryloylpropyltrimethoxysilane was selected as nanoparticle surface modifier because it is characterized by unsaturated end groups available to radical reactions, making possible to suppose their participation in the acrylic monomer polymerization. As a result of the above hypothesized reactions, a phase constituted by polyacrylic chains grafted onto modified silica surface was isolated. ²⁹Si and ¹³C solid‐state nuclear magnetic resonance experiments permitted to analyze this phase in terms of composition and chain mobility as well as to highlight interaction mechanisms occurring between growing PMMA oligoradicals and functional groups onto silica surface. It was demonstrated that this PMMA grafted onto silica surface acts as an effective coupling agent and assures a good dispersion of nanoparticles as well as a strong nanoparticle/matrix interfacial adhesion. As a result of strong interactions occurring between phases, a significant increase of the glass transition temperature was recorded. Finally, the abrasion resistance of PMMA in the hybrids was significantly improved as a result of a different abrasion propagation mechanism induced by silica particles thus overcoming one of the most serious PMMA drawback. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Thermal,mechanical, and morphological properties of novolac‐type phenolic resin blended with fullerenol polyurethane and linear polyurethane

Fullerenol polyurethane (C₆₀‐PU) and linear polyurethane (linear‐PU) modified phenolic resins were prepared in this study. Phenolic resin/C₆₀‐PU and phenolic resin/linear‐PU blends show good miscibility as a result of the intermolecular hydrogen bonding existing between phenolic resin and PU modifiers. DSC and thermogravimetric analysis methods were used to study the thermal properties of phenolic resin blended with different types of PUs. The intermolecular hydrogen bonding that existed between phenolic resin and C₆₀‐PU was investigated by Fourier transform infrared spectroscopy. The morphology and mechanical properties of phenolic resin/C₆₀‐PU and phenolic resin/linear‐PU blends were also investigated. The char yield of the modified phenolic resins decreased with increasing PU modifier content. Significant improvement in the toughness of the modified phenolic resins was observed. The improvements of impact strength were 27.4% for the phenolic resin/linear‐PU system and 54.3% for the phenolic resin/C₆₀‐PU system, respectively, both with 3 phr linear‐PU and C₆₀‐PU content. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2436–2443, 2001     

Poly(9‐undecyl‐9‐methyl‐fluorene) and poly(9‐pentadecyl‐9‐methyl‐fluorene): Synthesis,solution structure,and effect of side chain asymmetry on aggregation behavior

We report on solution aggregates and backbone conformation of poly(9‐undecyl‐9‐methyl‐fluorene) (PF1‐11) and poly(9‐pentadecyl‐9‐methyl‐fluorene) (PF1‐15), having two different side chains compared with poly(9,9‐dihexylfluorene) (PF6) and poly(9,9‐dioctylfluorene) (PF8) with two identical side chains. In the poor solvent methylcyclohexane (MCH), X‐ray scattering indicates that PF1‐11 and PF1‐15 appear as three‐dimensional aggregates (5–10 nm wide and thick), forming ribbon‐like agglomerates (correlation lengths of 100 nm). PF6 and PF8 appear as two‐dimensional aggregates (>10 nm wide and 2–3 nm thick) involving ribbon‐like agglomerates (correlation lengths much greater than 100 nm). Upon heating, all aggregates undergo a gel–sol transition which occurs at lower temperatures for PF1‐11 and PF1‐15 (<60°C) than for PF6 and PF8 (>80°C). In the good solvent toluene, PF1‐11 and PF1‐15 form networks of cylindrical particles. The mesh size and the cylinder radius are smaller in 24°C toluene (60 nm, 0.5 nm) than in 60°C MCH (300 nm, 1–2 nm). Nuclear magnetic resonance spectra in toluene‐d₈ together with density functional theory calculations suggest higher torsion angles between polymer repeat units for PF6, PF8, and PF1‐11 (less planar conformation) and a gauche arrangement of the dihedral angles between the bridge carbon atom and the side chain methylene groups in PF1‐15. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 826–837     

X‐ray powder diffraction of polymer/layered silicate nanocomposites: Model and practice

X‐ray powder diffraction in reflection (Bragg–Brentano parafocusing geometry) is extensively used to characterize the structure of polymer/layered silicate nanocomposites (PLSNs). The large basal spacings (d₀₀₁ > 2.0 nm) necessitates the collection of data at scattering angles (2θ) of less than 10°. The calculation of an ideal scattering profile for PLSNs provides an avenue to ascertain the influence of experimental parameters and the arrangement, organization, concentration, and composition of constituents on the experimentally observed pattern. This enables better experimental technique, more complete utilization of the scattering data, insight into inconsistencies between scattering and microscopy, and minimization of incorrect interpretation or overinterpretation of data. Because of the strong θ dependence of theoretical and experimental factors at low values of 2θ, careful sample preparation and data evaluation are necessary and should be complemented by microscopic observations, especially for PLSNs with low volume fractions of organically‐modified layered silicates (OLS) that are suspected of having exfoliated morphologies. X‐ray powder diffraction in reflection alone is insufficient to completely characterize and ascribe PLSN morphology. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1590–1600, 2002     

Structure and mechanical properties in drawn poly(l‐lactide)/clay hybrid films

Films composed of poly(l ‐lactide) (PLLA)/organophilic montmorillonite hybrids (PLACHs) have been prepared via a melt‐compounding process, which is followed by uniaxial drawing at 90°C in air. In addition, an enhancement of the mechanical properties of these drawn PLACH films, which is expected to differ depending on the drawn ratios, is also estimated by dynamic viscoelastic measurements. Three different organoclay concentrations in the hybrid of 3, 5, and 9 wt% were investigated. The structural parameters for the PLLA crystallites in the drawn films, such as the c‐axis orientation function (f_PLLA) and crystallite size, were measured by X‐ray diffraction, and their drawn ratio (λ) and clay concentration dependence were examined from a textural viewpoint. Another orientation function (f_clay) of the organoclay particles was obtained by transmission electron microscopy (TEM). The values of f_PLLA and crystallinity for PLLA sharply increased with λ for λ < 3, although f_clay was unchanged during the initial stage of elongation. In the high‐λ region (>5), the organoclay particles in the PLACHs started orienting themselves parallel to the draw direction. Copyright © 2008 John Wiley & Sons, Ltd.     

IR spectra studies of core‐shell type waterborne polyacrylate‐polyurethane microemulsions

The hydrogen bonds in films of the polyurethane and the core‐shell type polyacrylate‐polyurethane microemulsions have been studied by FTIR spectroscopy in the regions of  NH absorption and CO absorption. The effects on hydrogen bonds of the composition, the core‐shell ratio were revealed. At the same time, the relationship between the hydrogen bonds and the crosslinked structures (Type A and Type B) was discovered. The shifts of the  NH and CO stretching bands to higher frequencies and the shift of  NH bending bands to lower frequencies, with the increase of acetone CO number in the core, mean that the hydrogen bonds between the soft and hard segments, and those in the short‐range order in the hard segment phase, are broken. The dipole/dipole interaction which is supposed to exist between the acetone CO groups in the core and the urethane CO in the shell can change the hydrogen bond distribution in the shell, and at the same time, lead to hydrogen bonds between acetone CO in the core and the urethane  NH in the shell. Type A and B crosslinked structure between the core and the shell located at the interface of the core and the shell can confine the acetone CO within the crosslinking network, and Type B crosslinked structure also decreases the acetone CO numbers. These weaken the dipole/dipole interaction between the acetone CO and the urethane CO, and lead to the decrease of the effect of the acetone CO groups on the hydrogen bond distribution in the shell. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2642–2650, 1999     

Inorganic–organic hybrids involving poly(ε‐caprolactone) and silica network: Hydrogen‐bonding interactions and isothermal crystallization kinetics

Inorganic–organic hybrids mediated by hydrogen‐bonding interactions involving silicon oxide network and poly(ε‐caprolactone) (PCL) were prepared via an in situ sol–gel process of tetraethoxysilane in the presence of PCL. Fourier transform infrared spectroscopy indicated that there were hydrogen‐bonding interactions between carbonyls of PCL and silanol hydroxyls that were formed by incomplete polycondensation in the sol–gel process. In terms of the frequency shift of the hydroxyl stretching vibration bands, it is concluded that the strength of the interassociation between PCL and silicon oxide networks is weaker than that of the self‐association in the control silica network. The phenomenon of equilibrium melting point depression was observed for the PCL/silica system. The hybridization of PCL with silica network causes a considerable increase in the overall crystallization rate and dramatically influences the mechanism of nucleation and growth of the PCL crystallization. The analysis of isothermal crystallization kinetic data according to the Hoffman‐Lauritzen theory shows that with increasing silica content in the hybrids, the surface energy of extremity surfaces increases dramatically for the hybrids. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2594–2603, 2005