Structure and properties of poly(ethylene terephthalate)/Na+‐montmorillonite nanocomposites prepared by solid state shear milling (S3M) method

This article reported a novel technology, solid state shear milling (S³M), to prepare poly(ethylene terephthalate)/Na⁺‐montmorillonite nanocomposites using the pristine Na⁺‐MMT without organic modification so as to avoid the problem that the organic modifiers, used for MMT treatment will decompose at high processing temperature of PET, and the structure and properties of the obtained samples were investigated. XRD and TEM analyses showed that Na⁺‐MMT layers were partially delaminated and intercalated, and uniformly dispersed in the PET matrix when suffering from the strong three dimensional shearing forces of pan‐milling. DSC analysis showed that Na⁺‐MMT serves as a nucleating agent, increasing the crystallization rate as well as the crystallization temperature of PET. The properties such as thermal stability and tensile strength of the PET/Na⁺‐MMT nanocomposites prepared by S³M got remarkably improved. Solid state shear milling (S³M) method was a simple and efficient method to get polymer/Na⁺‐MMT nanocomposites with pretty good performances without organic modification of pristine Na⁺‐MMT. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 807–817, 2008     

Preparation and characterization of rigid poly (vinyl chloride)/MMT nanocomposites

In this article, a Haake torque rheometer equipped with an internal mixer is used to study the influence of the amount of sodium montmorillonite (Na⁺‐MMT) and organically modified MMT (O‐MMT) on the characteristics of rigid poly (vinyl chloride) (PVC)/Na⁺‐MMT and PVC/O‐MMT nanocomposites, respectively. It is observed that the fusion time and temperature of the rigid PVC/Na⁺‐MMT nanocomposites are decreased with increasing the amount of Na⁺‐MMT. On the contrast, the fusion time and temperature of the rigid PVC/O‐MMT nanocomposites are increased with increasing the amount of O‐MMT. Results of X‐ray diffraction (XRD) and transmission electron microscope (TEM) indicate that MMT is partially encapsulated and intercalated in the rigid PVC/Na⁺‐MMT nanocomposites. However, results of XRD and TEM show MMT is partially intercalated and exfoliated in the rigid PVC/O‐MMT nanocomposites. Tensile strength, yield strength, and elongation at break of the rigid PVC/MMT (including PVC/Na⁺‐MMT and PVC/O‐MMT) nanocomposites were improved simultaneously with adding 1–3 wt % Na⁺‐MMT or O‐MMT with respect to those of pristine PVC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1465–1474, 2005     

Expansion distribution of basal spacing of the silicate layers in polyaniline/Na+‐montmorillonite nanocomposites monitored with X‐ray diffraction

Polyaniline/Na⁺‐montmorillonite (Na⁺‐MMT) nanocomposites synthesized by in‐situ intercalative polymerization of aniline into Na⁺‐MMT are reported. The expansion distribution of basal spacing of the silicate layers upon the increase of the amount of aniline relative to Na⁺‐MMT is, for the first time, estimated from the square of the full‐width at half‐maximum (FWHM²) of XRD patterns. According to the FT‐IR frequency shift of the C‐N stretching vibration, the change in the basal spacing of the silicate layers is closely related to the degree of hydrogen bonding between polyaniline and the silicate basal surface in a confined geometry.     

Crystalline β‐structure of PHBV grown epitaxially on silicate layers of MMT

The poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV)/montmorillonite(MMT) nanocomposites were investigated by wide‐angle X‐ray scattering (WAXS). The aim of the investigation was solution intercalation of MMT with PHBV. Beside the usual orthorhombic unit cell, a stable pseudohexagonal β‐structure of PHBV was obtained. Well known β‐structure has one common WAXS reflection (d = 0.480 nm), which corresponds to the mean distance of PHBV chains in the pseudohexagonal structure. The new β‐structure has two diffraction peaks in the WAXS pattern. It is a three‐dimensionally ordered crystalline structure oriented in parallel with the silica layers of MMT. The new polymorphic form is supposed to be growing on the layers of MMT. Its layers serve as primary nucleation centers for epitaxial growth of the β‐structure. After annealing, this polymorphic form of PHBV disappears and it is transformed into the more stable α‐form leading to an enhanced total crystallinity of the polymer comprised in the nanocomposite. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 751–755, 2009     

Effects of TEMED and EDTA on the structural and mechanical properties of NIPAAm/Na+MMT composite hydrogels

N‐isopropyl acrylamide (NIPAAm) hydrogels are known as thermosensitive crosslinked polymer networks. In this work, the network parameters of their composites, i.e., NIPAAm/sodium montmorillonite (NIPAAm/Na⁺MMT) hydrogels synthesized by free radical solution polymerization in the presence of two different types of accelerator (tetramethyl ethylenediamine (TEMED) and ethylenediamine tetraacetic acid (EDTA)) and initiator (potassium persulphate (K₂S₂O₈) and cerium ammonium nitrate ((NH₄)₂Ce(NO₃)₆), Ce(IV)) using five different clay content (in the range of 1.0–5.0 wt % of total monomer concentration) at 25 °C were presented and discussed. FTIR spectra, XRD patterns, SEM photographs, and network parameters of the samples indicated that the presence of COOH groups on EDTA molecules was resulted in the formation of exfoliated structures and the activity of EDTA/KPS redox pair was higher than those of TEMED/KPS and EDTA/Ce (IV) pairs. The compression moduli (G) of the hydrogels initiated with EDTA/Ce(IV) redox pair showed smooth and continual changings with increase in Na⁺MMT content (for swelling equilibrium at 25 °C) on the contrary of EDTA/KPS and TEMED/KPS pairs. It might be related to low initiator efficiency of cerium ammonium nitrate than KPS molecules, having higher effective crosslinking density with increasing clay content. On the other hand, the G moduli of NIPAAm/Na⁺MMT hydrogels (above their phase transition temperature) initiated with TEMED/KPS redox pair were higher than the others because of the more hydrophobic nature of TEMED molecules. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1256–1264, 2010     

Preparation and characterization of rigid poly(vinyl chloride)/MMT nanocomposites. II. XRD,morphological and mechanical characteristics

A Haake torque rheometer equipped with an internal mixer is used to study the influence of the amount of sodium montmorillonite (Na⁺‐MMT) and organically modified MMT (O‐MMT) on X‐ray diffraction (XRD), morphology, and mechanical characteristics of rigid poly (vinyl chloride) (PVC)/Na⁺‐MMT and PVC/O‐MMT nanocomposites, respectively. Results of XRD and transmission electron microscopy (TEM) indicate that MMT is partially encapsulated and intercalated in the rigid PVC/Na⁺‐MMT nanocomposites. However, results of XRD and TEM show MMT is partially intercalated and exfoliated in the rigid PVC/O‐MMT nanocomposites. Tensile strength, yield strength, and elongation at break of the rigid PVC/MMT nanocomposites were improved simultaneously with adding 1–3 wt % Na⁺‐MMT or O‐MMT with respect to that of pristine PVC. However, the addition of Na⁺‐MMT or O‐MMT should be kept as not more than 3 wt % to optimize the mechanical properties and the processing stability of the rigid PVC/MMT nanocomposites. SEM micrographs of the fractured surfaces of the rigid PVC/Na⁺‐MMT and PVC/O‐MMT nanocomposites both before and after tensile tests were also illustrated and compared. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2145–2154, 2006     

Properties of Nylon‐6/Na+‐Montmorillonite Nanocomposites Obtained by Hydrolyzed Ring‐Opening Polymerization

Summary: Nylon‐6/Na⁺‐montmorillonite (MMT) nanocomposites (NNNs) are synthesized by a hydrolyzed ring‐opening polymerization. At a loading of only 2 wt.‐% MMT, the tensile modulus, the flexural modulus, and the heat distortion temperature of the NNNs exhibit increases of nearly 20%, 60%, and 63 °C, respectively. Compared with that of neat nylon‐6, the temperature of the main α‐relaxation (T_α) of the NNNs is shifted 3.6 °C toward higher temperatures and two β‐relaxation peaks are observed. Another interesting phenomenon is that there is a new melting peak (at about 206 °C) for the NNNs.

DSC second heating curves of neat nylon‐6 (N6), nylon‐6/Na⁺‐MMT nanocomposites with highly swollen Na⁺‐MMT (NHM), and nylon‐6/Na⁺‐MMT nanocomposites with slightly swollen Na⁺‐MMT (NSM) with various amounts of Na⁺‐MMT.     

Preparation and properties of organo‐modifier free PET/MMT nanocomposites via monomer intercalation and in situ polymerization

In order to prevent the properties, especially transparency, color and health security, of PET/clay nanocomposites from being deteriorated due to the thermal degradation of clay organo‐modifer, we had directly modified sodium montmorillonite (Na⁺‐MMT) with PET's monomer, bis (hydroxyethyl) terephthalate (BHET) which had a degradation temperature higher than 400°C, and successfully prepared the hybrids via in situ polymerization. Nanodispersion of clay and the intercalated morphology were determined, and compared with PET/Na⁺‐MMT hybirds in which Na⁺‐MMT was directly added without any treatment. Improved mechanical properties and T_g were observed for the prepared PET/ BHET‐modified clay composites. More importantly, the film produced from the composites had the same transparency as that of pure PET even when 2 wt% of clay was added. Non‐isothermal and isothermal crystallization experiments showed a very good neculation capability of the nano‐dispersed clay, particularly at higher crystallization temperatures. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and Rheology of Intercalated Polystyrene/Na+‐Montmorillonite Nanocomposites

Polystyrene (PS)/clay nanocomposites were synthesized by the emulsion polymerization of styrene in the presence of sodium ion‐exchanged montmorillonite (Na⁺‐MMT), demonstrating that the strongly hydrophobic PS was intercalated into the hydrophilic silicate layers. The nanocomposites were examined by means of X‐ray diffraction, transmission electron microscopy, thermogravimetric analysis. The rheological properties of the PS/Na⁺‐MMT nanocomposites were also studied to exhibit more pronounced shear thinning behavior with increasing clay content.     

Aggregative structure of the 1‐octadecyl‐3‐methylimidazolium cation in the interlayer of montmorillonite and its effect on polypropylene melt intercalation

A series of organomontmorillonites were synthesized from pristine sodium montmorillonite via ion exchange in toluene with 1‐octadecyl‐3‐methylimidazolium chloride, a kind of ionic liquid with high thermal stability, as a modifier. The amount and aggregative state of the 1‐octadecyl‐3‐methylimidazolium cation ([C18mim]⁺) adsorbed in the interlayer of organomontmorillonite (MMT) were investigated with thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy, X‐ray diffraction (XRD), and differential scanning calorimetry. XRD patterns showed that [C18mim]⁺ was successfully intercalated into the interlayer of MMT, and the interlayer distances of the clays increased dramatically. On the basis of the TGA results, three types of arrangement models of [C18mim]⁺ could be seen, and they were related to the loading level of [C18mim]⁺ in the gallery of MMT. The effects of the aggregative structure of [C18mim]⁺ in the interlayer of MMT on polypropylene melt intercalation was also examined. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1252–1259, 2007     

Sodium 2‐oxo‐3‐semicarbazono‐2,3‐dihydro‐1H‐indole‐5‐sulfonate dihydrate

The title compound, Na⁺·C₉H₇N₄O₅S⁻·2H₂O, presents a Z configuration around the imine C=N bond and an E configuration around the C(O)NH₂ group, stabilized by two intra­molecular hydrogen bonds. The packing is governed by ionic inter­actions between the Na⁺ cation and the surrounding O atoms. The ionic unit, Na⁺ and 2‐oxo‐3‐semicarbazono‐2,3‐dihydro‐1H‐indole‐5‐sulfonate, forms layers extending in the bc plane. The layers are connected by hydrogen bonds involving the water mol­ecules.     

Atypical transition temperature dependence of poly(N‐isopropylacrylamide) and poly(N‐isopropylacrylamide‐co‐acrylamide) nanocomposites on the content of exfoliated montmorillonites

Exfoliated montmorillonite (MMT)/poly(N‐isopropylacrylamide) (PNIPAAm) and MMT/poly(N‐isopropylacrylamide‐co‐acrylamide) [P(NIPAAm‐co‐AAm)] nanocomposites were fabricated by soap‐free emulsion polymerization. Interestingly, as the content of MMT was increased from 0 to 10 wt %, the glass transition temperature of MMT/PNIPAAm was decreased from 145 to 122 °C, whereas that of the MMT/P(NIPAAm‐co‐AAm) increased from 95 to 153 °C. Although the lower critical solution temperature (LCST) of 32 °C for the MMT/PNIPAAm nanocomposites in aqueous solutions was slightly increased with the content of MMT, that of the MMT/P(NIPAAm‐co‐AAm) was decreased from 70 to 65 °C. A mechanism that the hydrogen bonds between the amide groups of PNIPAAm were interfered by the exfoliated MMT nano‐platelets for the MMT/PNIPAAm nanocomposites and the preferred absorption of acrylamide units to the MMT nanoplatelets rather than N‐isopropylacrylamide in the MMT/P(NIPAAm‐co‐AAm) nanocomposites was suggested to interpret these unusual transition behavior. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 524–530, 2009     

Aggregation behavior of poly(γ‐benzyl‐L‐glutamate)‐b‐polyisoprene‐b‐poly(γ‐benzyl‐L‐glutamate) rod‐coil‐rod triblock copolymer in N,N‐dimethylformamide

Solution property of poly(γ‐benzyl‐L ‐glutamate)‐b‐polyisoprene‐b‐poly(γ‐benzyl‐L ‐glutamate) (GIG copolymer) was studied by using dynamic light scattering and static light scattering for N,N‐dimethylformamide (DMF) solution and DMF/toluene mixed solutions. GIG copolymer proved to aggregate in DMF and under DMF‐rich condition, that is, high‐polar region. The aggregate decreased in size, and completely disappeared under toluene‐rich condition, that is, low‐polar region. The correlation between solubility parameter and aggregate size of GIG copolymer in the DMF/toluene solution systems quantitatively demonstrated how strongly polarity caused by hydrogen bond made an impact on the aggregation behavior. Because the main driving force to the aggregation under DMF‐rich condition originates with polyisoprene (PIP) blocks, the aggregate in DMF is considered to be a core‐shell micelle consisting of flexible PIP core surrounded by rigid poly(γ‐benzyl‐L ‐glutamate) (PBLG) shell. The values of dimensionless parameter ρ, defined as the ratio of radius of gyration 〈S²〉^1/2 to hydrodynamic radius R_H, revealed that a single chain of GIG copolymer had the form of rigid rod with flexibility, that is, once‐broken rod, caused by the incorporation of a flexible PIP chain between two rigid PBLG rods in the DMF/toluene solution system. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1740–1748, 2010     

A Highly K+‐Selective Fluorescent Probe – Tuning the K+‐Complex Stability and the K+/Na+ Selectivity by Varying the Lariat‐Alkoxy Unit of a Phenylaza[18]crown‐6 Ionophore

A desirable goal is to synthesize easily accessible and highly K⁺/Na⁺‐selective fluoroionophores to monitor physiological K⁺ levels in vitro and in vivo. Therefore, highly K⁺/Na⁺‐selective ionophores have to be developed. Herein, we obtained in a sequence of only four synthetic steps a set of K⁺‐responsive fluorescent probes 4 , 5 and 6 . In a systematic study, we investigated the influence of the alkoxy substitution in ortho position of the aniline moiety in π‐conjugated aniline‐1,2,3‐triazole‐coumarin‐fluoroionophores 4 , 5 and 6 [R=MeO ( 4 ), EtO ( 5 ) and iPrO ( 6 )] towards the K⁺‐complex stability and K⁺/Na⁺ selectivity. The highest K⁺‐complex stability showed fluoroionophore 4 with a dissociation constant K_d of 19 mm , but the K_d value increases to 31 mm in combined K⁺/Na⁺ solutions, indicating a poor K⁺/Na⁺ selectivity. By contrast, 6 showed even in the presence of competitive Na⁺ ions equal K_d values (K_d^K+=45 mm and K_d^K+/Na+=45 mm ) and equal K⁺‐induced fluorescence enhancement factors (FEFs=2.3). Thus, the fluorescent probe 6 showed an outstanding K⁺/Na⁺ selectivity and is a suitable fluorescent tool to measure physiological K⁺ levels in the range of 10–80 mm in vitro. Further, the isopropoxy‐substituted N‐phenylaza[18]crown‐6 ionophore in 6 is a highly K⁺‐selective building block with a feasible synthetic route.     

Poly(γ‐benzyl‐L‐glutamate)‐functionalized single‐walled carbon nanotubes from surface‐initiated ring‐opening polymerizations of N‐carboxylanhydride

Single‐walled carbon nanotubes (SWCNTs) have been functionalized with poly(γ‐benzyl‐L ‐glutamate) (PBLG) by ring‐opening polymerizations of γ‐benzyl‐L ‐glutamic acid‐based N‐carboxylanhydrides (NCA‐BLG) using amino‐functionalized SWCNTs (SWCNT‐NH₂) as initiators. The SWCNT functionalization has been verified by FTIR spectroscopy and transmission electron microscopy. The FTIR study reveals that surface‐attached PBLGs adopt random‐coil conformations in contrast to the physically absorbed or bulk PBLGs, which exhibit α‐helical conformations. Raman spectroscopic analysis reveals a significant alteration of the electronic structure of SWCNTs as a result of PBLG functionalization. The PBLG‐functionalized SWCNTs (SWCNT‐PBLG) exhibit enhanced solubility in DMF. Stable DMF solutions of SWCNT‐PBLG/PBLG with a maximum SWCNTs concentration of 259 mg L^?1 can be readily obtained. SWCNT‐PBLG/PBLG solid composites have been characterized by differential scanning calorimetry, thermogravimetric analysis, wide/small‐angle X‐ray scattering (W/SAXS), scanning electron microscopy, and polarized optical microscopy for their thermal or morphological properties. Microfibers containing SWCNT‐PBLG and PBLG can also be prepared via electrospinning. WAXS characterization reveals that SWCNTs are evenly distributed among PBLG rods in solution and in the solid state where PBLGs form a short‐range nematic phase interspersed with amorphous domains. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2340–2350, 2010     

Direct or indirect influence of triphenyl‐lead on activity of Na+/K+‐ATPase

We have studied the effect of triphenyl‐lead chloride on the lipid phase of erythrocyte membranes, on lipid monomolecular layers and Na⁺/K⁺‐ATPase of the microsomal fraction of rat brain. It was found that the haemolytic effect induced by this compound occurs when its concentration exceeds 30 µM . The minimal lead concentration inducing measurable effects in monomolecular lecithin layers is about 1 µM . Inhibition of Na⁺/K⁺‐ATPase activity begins at a concentration exceeding 0.5 µM . Maximum inhibition is observed at around 40 µM —a concentration at which haemolysis also occurs. It can thus be thought that at very low lead concentrations the main (or exclusive) role in modifying membrane function is played by direct interaction between lead and the sulphydryl groups of ATPase, whereas at higher concentrations two effects seem to overlap: direct interaction between lead and enzymic proteins via their sulphydryl groups and as indirect influence on the proteins via changes in the organization of the lipid phase of the membrane. Copyright © 2000 John Wiley & Sons, Ltd.     

Dispersibility of clay and crystallization kinetics for in situ polymerized PET/pristine and modified montmorillonite nanocomposites

Nanocomposite materials composed of poly (ethylene terephthalate) (PET) and montmorillonite (MMT) clays were prepared by in situ polymerization. Samples consisted of PET blended with various quantities of either pristine (Na⁺‐MMT) or organically modified MMT (A10‐MMT). The morphology and thermal and mechanical properties were evaluated for each sample. TEM micrographs, acquired at a 20 nm resolution, provide direct evidence of exfoliation of the clay particles into the PET matrix and show the effect of the alkyl‐modifier on clay dispersibility. The dispersion of PET/A10‐MMT was greater than that observed for the PET/Na⁺‐MMT nanocomposites. The greatest degree of exfoliation occurred for PET/A10‐MMT 0.5 wt %. However, PET/Na⁺‐MMT exhibited higher crystallization temperatures and rates suggesting that Na⁺‐MMT is a more efficient nucleating agent. Both mechanically and thermally, PET/A10‐MMT nanocomposites exhibited superior properties over pure PET. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1022–1035, 2008     

syn and anti conformations in 2‐hydroxy‐5‐[(E)‐(4‐nitrophenyl)diazenyl]benzoic acid and two related salts

The crystal structures of 2‐hydroxy‐5‐[(E)‐(4‐nitrophenyl)diazenyl]benzoic acid, C₁₃H₉N₃O₅, (I), ammonium 2‐hydroxy‐5‐[(E)‐phenyldiazenyl]benzoate, NH₄⁺·C₁₃H₉N₂O₃⁻, (II), and sodium 2‐hydroxy‐5‐[(E)‐(4‐nitrophenyl)diazenyl]benzoate trihydrate, Na⁺·C₁₃H₈N₃O₅⁻·3H₂O, (III), have been determined using single‐crystal X‐ray diffraction. In (I) and (III), the phenyldiazenyl and carboxylic acid/carboxylate groups are in an anti orientation with respect to each other, which is in accord with the results of density functional theory (DFT) calculations, whereas in (II), the anion adopts a syn conformation. In (I), molecules form slanted stacks along the [100] direction. In (II), anions form bilayers parallel to (010), the inner part of the bilayers being formed by the benzene rings, with the –OH and –COO⁻ substituents on the bilayer surface. The NH₄⁺ cations in (II) are located between the bilayers and are engaged in numerous N—H...O hydrogen bonds. In (III), anions form layers parallel to (001). Both Na⁺ cations have a distorted octahedral environment, with four octahedra edge‐shared by bridging water O atoms, forming [Na₄(H₂O)₁₂]⁴⁺ units.     

Side‐chain polypseudorotaxanes by threading cucurbit[7]uril onto poly‐N‐n‐butyl‐N′‐(4‐vinylbenzyl)‐4,4′‐bipyridinium bromide chloride: Synthesis,characterization, and properties

A novel side‐chain polypseudorotaxanes P4VBVBu/CB[7] was synthesized from poly‐N‐n‐butyl‐N′‐(4‐vinylbenzyl)‐4,4′‐bipyridinium bromide chloride (P4VBVBu) and cucurbit [7]uril (CB[7]) in water by simple stirring at room temperature. CB[7] beads are localized on viologen units in side chains of polypseudorotaxanes as shown by ¹H NMR, IR, XRD, and UV–vis studies, and it is considered that the hydrophobic and charge‐dipole interactions are the driving forces. TGA data show that thermal stability of the polypseudorotaxanes increases with the adding of CB[7] threaded. DLS data show that P4VBVBu and CB[7] could form polypseudorotaxanes, and the average hydrodynamic radius of the polypseudorotaxanes increases with increasing the concentration of CB[7]. The typical cyclic voltammograms indicate that the oxidation reduction characteristic of P4VBVBu is remarkably affected by the addition of CB[7] because of the formation of polypseudorotaxanes and the shielding effects of CB[7] threaded on the viologen units of polypseudorotaxanes. With the increase of the concentration of KBr or K₂SO₄, the formation of the polypseudorotaxanes was inhibited due to the shielding effects of both Br^? or SO to viologen ion and K⁺ to CB[7] by UV–vis. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2135–2142, 2010     

Isothermal crystallization behavior of exfoliated‐PP/IMMT nanocomposites via in situ polymerization

Highly exfoliated isotactic‐polypropylene/alkyl‐imidazolium modified montmorillonite (PP/IMMT) nanocomposites have been prepared via in situ intercalative polymerization. TEM and XRD results indicated that the obtained composites were highly exfoliated PP/IMMT nanocomposites and the average thickness of IMMT in PP matrix was less than 10 nm, and the distance between adjacent IMMT particles was in the range of 20–200 nm. The isothermal crystallization kinetics of highly exfoliated PP/IMMT nanocomposites were investigated by using differential scanning calorimeter(DSC) and polarized optical microscope (POM). The crystallization half‐time t_1/2, crystallization peak time t_max, and the Avrami crystallization rate constant K_n showed that the nanosilicate layers accelerate the overall crystallization rate greatly due to the nucleation effect, and the crystallization rate was increased with the increase in MMT content. Meanwhile, the crystallinity of PP in nanocomposites decreased with the increase in clay content which indicated the PP chains were confined by the nanosilicate layers during the crystallization process. Although the well‐dispersed silicate layers did not have much influence on spherulites growth rate, the nucleation rate and the nuclei density increased significantly. Accordingly, the spherulite size decreased with the increase in MMT content. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2215–2225, 2009