茂金属催化苯乙烯间规聚合物的颗粒形态

以均相单茂钛化合物［Cp*Ti(OPh)₃ 和Cp*Ti(OPhOMe)₃］为主催化剂,配以烷基铝氧烷（MAO）和三异丁基铝(TIBA),进行了苯乙烯的本体间规聚合.研究发现,聚合过程中生成聚合物的快速结晶对于避免反应体系的凝胶化,制得颗粒状产物十分重要.但正因为这种结晶成核机理,使所得颗粒的形貌极不规整,调控也十分困难.聚合过程中sPS种子的加入没有明显改善生成聚合物的颗粒形态.但当聚合体系中引入少量其他聚合物后,得到了较为规整的sPS颗粒,尤其当加入的聚合物与无定形sPS热力学不相容时（如mEPDM）,得到了十分规则的球状颗粒.     

Rate and molecular weight distribution modeling of syndiospecific styrene polymerization over silica-supported metallocene catalyst

The kinetics of syndiospecific polymerization of styrene over silica-supported Cp^∗Ti(OCH₃)₃/MAO catalyst has been investigated through experimentation and theoretical modeling. At low monomer concentrations, the polymerization rate increases almost linearly with monomer conversion, but the reaction rate becomes independent of monomer concentration at high bulk phase monomer concentrations. A kinetic model that incorporates the monomer partition effect between the solid and the liquid phases has been proposed. The model simulations show that the observed non-linear kinetics can be adequately modeled by the monomer partition model. The polymer molecular weight has also been found to increase with the monomer concentration and the polymer molecular weight distribution (MWD) is quite broad, suggesting that the catalytic behavior deviates from the single site catalytic polymerization model. The MWD broadening is modeled by a two-site kinetic model and a good agreement between the model and the experimental data has been obtained.     

Effects of crystallization temperature on the polymorphic behavior of syndiotactic polystyrene

The influence of crystallization temperature on formation of the α- and β-form crystals of syndiotactic polystyrene (sPS) was investigated by X-ray diffraction and non-isothermal differential scanning calorimetry analysis. For sPS samples without any thermal history, the crystallization temperature must be the intrinsic factor controlling the formation the α and β-form crystals. Being crystallized at different cooling rate from the melt, sPS forms the β-form crystal until the temperature cooled down to about 230 °C, and α-form crystal can only be obtained when the temperature was below about 230 °C.     

The atactic polystyrene molecular weight effect on the thermal properties and crystal structure of syndiotactic polystyrene/atactic polystyrene blends

This work examined how the molecular weight of atactic polystyrene (aPS) affects the thermal properties and crystal structure of syndiotactic polystyrene (sPS)/aPS blends using differential scanning calorimetry, polarized light microscopy and wide angle X-ray diffraction (WAXD) technique. For comparative purposes, the structure and properties of the parent sPS was also investigated. The experimental results indicated that these blends showed single glass transition temperatures (T_gs), implying the miscibility of these blends in the amorphous state regardless of the aPS molecular weight. The non-isothermal and isothermal melt crystallization of sPS were hindered with the incorporation of aPSs. Moreover, aPS with a lower molecular weight caused a further decrease in the crystallization rate of sPS. Complex melting behavior was observed for parent sPS and its blends as well. The melting temperatures of these blends were lower than those of the parent sPS, and they decreased as the molecular weight of aPS decreased. Compared with the results of the WAXD study, the observed complex melting behavior resulted from the mixed polymorphs (i.e. the α and β forms) along with the melting-recrystallization-remelting of the β form crystals during the heating scans. The degree of melting-recrystallization-remelting phenomenon for each specimen was dependent primarily on how fast the sPS crystals were formed instead of the incorporation of aPSs. Furthermore, the existence of aPS in the blends, especially the lower molecular weight aPS, apparently reduced the possibility of forming the less stable α form in the sPS crystals.     

Isothermal crystallization, melting behavior and crystalline morphology of syndiotactic polystyrene blends with highly-impact polystyrene

Syndiotactic polystyrene (sPS) blends with highly-impact polystyrene (HIPS) were prepared with a twin-screw extruder. Isothermal crystallization, melting behavior and crystalline morphology of sPS in sPS/HIPS blends were investigated by differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarized optical microscopy (POM). Experimental results indicated that the isothermal crystallization behavior of sPS in its blends not only depended on the melting temperature and crystallization temperature, but also on the HIPS content. Addition of HIPS restricted the crystallization of sPS melted at 320 °C. For sPS melted at 280 °C, addition of low HIPS content (10 wt% and 30 wt%) facilitated the crystallization of sPS and the formation of more content of α-crystal. However, addition of high HIPS content (50 wt% and 70 wt%) restricted the crystallization of sPS and facilitated the formation of β-crystal. More content of β-crystal was formed with increase of the melting and crystallization temperature. However, α-crystal could be obtained at low crystallization temperature for the specimens melted at high temperature. Addition of high HIPS content resulted in the formation of sPS spherulites with less perfection.     

Physical transitions and nascent morphology of syndiotactic polystyrene in slurry polymerization with embedded CpTi(OMe)3/methyl aluminoxane catalyst

The physical transitions and nascent morphology of syndiotactic polystyrene (sPS) synthesized over heterogeneized embedded Cp^*Ti(OMe)₃/MAO catalyst in n-heptane slurry polymerization have been investigated. The homogeneous metallocene catalyst is heterogenized by embedding active titanium sites into an sPS prepolymer phase. At low styrene concentrations, the reaction mixture is well-dispersed slurry of sPS particles and at high styrene concentrations, swollen sPS particles form aggregates that become a wet powder phase. For a wide range of styrene concentrations, no global gelation occurs with the embedded catalyst. Complex nascent morphology of sPS polymers is also presented. Scanning electron microscopic images show that spherical as well as irregular-shaped microparticles, films, and fibers are formed and that particle generation and growth mechanisms are different from that of heterogeneously catalyzed α-olefin polymerization processes.     

Miscible blends of syndiotactic polystyrene and atactic polystyrene. Part 1. Lamellar morphologies and diluent segregation

Lamellar morphologies of melt-crystallized blends of syndiotactic polystyrene (sPS, weight-average molecular weight ) and atactic polystyrene (aPS, M_w=100k) have been investigated using small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). sPS/aPS blends with various compositions were prepared and crystallized isothermally at 250 °C prior to morphological studies. Due to the proximity in the densities of the crystal and amorphous phases, a weak SAXS reflection associated with lamellar microstructure was obtained at room temperature. In addition, strong diffuse scattering at low scattering vectors was evidently observed and its appearance may obscure the intensity maximum associated with the lamellar features, leading to the difficulties in determining the microstructure of the blends. To enhance the density contrast, SAXS intensities at an elevated temperature of 150 °C were measured as well to deduce the morphological results with better precision. Based on the Debye-Bueche theory, the intensities of the diffuse scattering were estimated and subtracted from the observed intensities to obtain the scattering contribution exclusively from the lamellar microstructure. Morphological parameters of the sPS/aPS blends were derived from the one-dimensional correlation function. On addition of aPS, no significant changes in the lamellar thickness have been found and the derived lamellar thicknesses are in good agreement with TEM measurements. Segregation of rejected aPS components during sPS crystallization was evidently observed from TEM images which showed aPS pockets located between sPS lamellar stacks and distributed uniformly in the bulk samples, leading to the interfibrillar segregation.     

Effect of chain-length of n-alkane on solvent-induced crystallization and solvent exchange phenomenon in syndiotactic polystyrene

The effect of molecular size and the vapor pressure of a series of n-alkanes as a solvent on solvent-induced crystallization of amorphous sPS and also the solvent exchange phenomenon in the δ form of syndiotactic polystyrene (sPS) were investigated by means of FT-IR spectroscopy and X-ray diffraction. The crystallization of amorphous sPS was found to be very much influenced by the molecular size and the vapor pressure of the n-alkanes used. At room temperature, n-alkanes with six and seven carbon atoms crystallize the sPS into the δ form, whereas the longer n-alkanes did not induce the crystallization of the amorphous sPS. By increasing the crystallization temperature to 50 °C, the vapor pressure of n-alkanes increases and as a result n-alkanes with eight to ten carbon atoms crystallize the amorphous sPS into the γ form unlike the cases of n-hexane and n-heptane. On further increasing the chain-length of n-alkanes to n-tridecane and n-hexadecane, no crystallization of amorphous sPS was observed even at 50 °C. By keeping the crystallization behavior in mind, we used these n-alkanes to exchange the existing solvent in the δ form of sPS/chloroform complex. n-Alkanes with six and seven carbon atoms easily replace the chloroform enclosed in the crystal lattice at room temperature and the d₀₁₀ lattice spacing was found to increase according to the molecular size of the solvent used in the exchange process. n-Alkanes with eight to ten carbon atoms could also replace the chloroform enclosed in the crystal lattice at room temperature. But in this case the d₀₁₀ lattice spacing was found to be similar or lower than that of the δ form of sPS/chloroform complex and a new reflection was observed 2θ = 6.6°, indicating the formation of the ? form. On the other hand, longer n-alkanes (C13 and C16) did not intrude into the cavities of the δ form at room temperature. By increasing the solvent exchange temperature to 50 °C, the longer n-alkanes (C13 and C16) also replaced the existing chloroform in the δ form and structure transformed to the ? form. In this way, we found that the crystallization and solvent exchange process of sPS using n-alkanes is quite complicated and depends strongly on the chain-length of n-alkane molecule.     

Influence of host preparation method on the structural phase transitions of syndiotactic polystyrene upon the guest exchange with n-alkanes

The starting morphology used for the preparation of the syndiotactic polystyrene (sPS)/solvent complex, has a significant role in facilitating the phase transitions of the host structure upon guest exchange process. This effect was studied on the structural changes of sPS, using guest exchange process, with a series of n-alkanes, and analyzed by X-ray diffraction and Fourier transform infrared spectroscopy. SPS–solvent complexes (monoclinic δ form) were prepared with different starting morphologies i.e. amorphous, α and γ forms using toluene and chloroform as guests. Upon guest exchange process (performed by dipping the samples in a series of n-alkanes viz. n-octane to n-decane), toluene treated amorphous and α form samples (i.e. monoclinic δ form) transformed into the triclinic δ form irrespective of the starting morphology. However, the toluene treated γ form transformed back to the γ form in presence of n-alkanes. Chloroform treated amorphous sample (i.e. monoclinic δ form), however, converted to a mixture of δ form (triclinic) and ε form, while chloroform treated α and γ forms transformed into triclinic δ form and ε form, respectively. Besides host preparation method, influence of starting δ form crystallinity on the guest exchange process was also examined.     

Polymorphism and mechanical properties of syndiotactic polystyrene films

The dynamic-mechanical behaviour and the tensile moduli of unstretched and stretched semicrystalline s-PS films, presenting different polymorphic forms (α, γ, δ and clathrate) but similar crystallinity and orientation, have been compared. The main aim is to elucidate the possible influence of different crystalline phases, being largely different in chain conformation and density, on mechanical properties of s-PS semicrystalline samples. For unstretched films presenting a preferential perpendicular orientation of the chain axes, the highest elastic modulus is observed for films with the high density γ phase while for uniaxially oriented films the highest modulus is observed for films with the trans-planar α phase. As for the clathrate films, the guest molecules when only included into the crystalline clathrate phase, have no plasticizing effect.     

Nucleation effect on polymorphism of melt-crystallized syndiotactic polystyrene

The main purpose of this study is to examine the effect of nucleation on the formation of polymorphism in melt-crystallized syndiotactic polystyrene (sPS). By depressing the nucleation barrier (i.e., introducing nucleating agent), the tendency of forming, a metastable crystalline phase, α crystal, significantly increased. The metastability of crystalline phase was dependent upon the nucleation process in which the lower nucleation barrier led to the formation of metastable phase. Consistently, by crystallizing under shearing, the formation of α crystal dominated the crystalline polymorphism. Herein we suggest a practical method to control the polymorphism of melt-crystallized sPS.     

Preparation and characterization of maleic anhydride-functionalized syndiotactic polystyrene

The free radical-induced grafting of maleic anhydride (MA) onto syndiotactic polystyrene (sPS) has been accomplished in the solution process by using 1,1,2-trichloroethane as solvent and dicumyl peroxide as free radical initiator. The amount of MA grafted on sPS was evaluated by a titration method. Grafted products separated from the reaction mixture were purified and analyzed. Fourier transform infrared spectroscopy and ¹H NMR studies indicate that MA attaches to the sPS in the form of single succinic anhydride rings as well as short oligomers. The results obtained by GPC analysis suggest that the degradation and chain extension reaction do not occur under the reaction conditions. Moreover, the crystallization behavior of MA-functionalized sPS was also studied by means of differential scanning calorimetry. It was found that the crystallization behavior of the grafted polymer exhibited somewhat differences in comparison to the neat sPS. The MA-functionalized sPS crystallizes at higher rate than the unmodified polymer, on the other hand, the degree of crystallinity (X_c) are lowered by the presence of the MA grafts.     

Carbon nanocapsules-reinforced syndiotactic polystyrene nanocomposites: Crystallization and morphological features

Syndiotactic polystyrene (sPS) composites filled with well-dispersed carbon nanocapsules (CNC) were prepared through solution blending along with ultrasonication. Several analytic techniques, including DSC, FTIR, PLM, WAXD, TEM, and TGA were performed to reveal the CNC effects on the crystallization, morphology and the thermal degradation of the as-prepared sPS/CNC composites. Addition of CNC was found to favor the crystalline modification of β-form sPS and depress the α-form ones. For the dynamic crystallization, a gradual reduction of cold-crystallization temperature of the α-form sPS was observed by increasing the CNC content although the glass transition temperature remained unchanged (∼96 °C). In contrast, the melt-crystallization temperature of the β-form sPS was elevated from 238 °C for the neat sPS to 251 °C for the 99/5 composite in spite of the fact that the equilibrium melting temperature (∼290 °C) determined from the linear Hoffman-Weeks plot was irrelevant with CNC concentrations. The former was attributable to the formation of an effective heat-conduction path to trigger an earlier overall crystallization. On the other hand, the latter resulted from the enhanced nucleation sites due to the presence of uniformly dispersed CNCs. Results of the isothermal crystallization of the β-form sPS concluded that the presence of 1% CNCs led to a significant increase in the crystallization rate as much as an order of magnitude. Moreover, the Avrami exponent changed to ∼2.0 from a value of 2.8 for the neat sPS, suggesting a different crystallization mechanism involved. At a given crystallization temperature, PLM results showed a negligible variation in the crystal growth rates and a decrease in spherulitic sizes, indicating that nucleation played the key role in enhancing the crystallization rate. For samples isothermally crystallized at 260 °C, the lamellar thickness was constant to be ∼7.2 nm regardless of the CNC content. Due to the enhanced nucleation, however, lamellar stacks were more randomly oriented and its lateral dimensions became shorter with increasing CNC contents. For composites with more than 1 wt% CNC, the crystallizability of sPS chains was reduced and the annealing peak located ca. 4 °C higher than the crystallization temperature became more evident, suggesting the plausible formation of micro-crystals in between the lamellar stacks. The TGA results illustrated that a better thermal stability was reached for the CNC-filled sPS composites.     

Simultaneous presence of positive and negative spherulites in syndiotactic polystyrene and its blends with atactic polystyrene

Crystal growth rates of syndiotactic polystyrene (sPS) and its blends with atactic polystyrene (aPS) at various temperatures (T_c) were measured using a polarized optical microscope (POM). In addition to the positively birefringent spherulites and axilites (P-spherulites and P-axilites) which are predominantly observed, small population of negatively birefringent spherulites (N-spherulites) is also detected in the neat sPS as well as in the sPS/aPS blends at a given T_c. Both P-spherulites and P-axilites possess a similar growth rate, whereas a smaller growth rate is found for N-spherulites at all T_c and samples investigated. Melting behavior of individual P- and N-spherulites was feasibly traced using hot-stage heating and a highly sensitive CCD through the decay of transmitted light intensity under cross-polars. Both P- and N-spherulites demonstrate exactly the same melting behavior under POM, which well corresponds to the differential scanning calorimetry measurements, suggesting no difference in lamellar thickness distribution or crystal perfection within P- and N-spherulites. Lamellar morphologies within spherulites were extensively investigated using transmission electron microscopy (TEM) as well as scanning electron microscopy (SEM). Results obtained from TEM and SEM show that the lamellar stacks within P-spherulites grow radially, whereas those within N-spherulites are packed relatively tangentially. The growth of P-spherulites is associated with the gradual increase of lamellae' lateral dimensions which follows the conventional theory of growth mechanism. However, the measured growth rate of N-spherulites is relevant to the gradual deposition of new lamellar nuclei adjacent to the fold surfaces of already-existing lamellar stacks. The difference in measured growth rate between P- and N-spherulites is attributed to the different energy barrier required to develop stable nuclei. Based on the exhaustive TEM and SEM observations, plausible origin of N-spherulites is provided and discussed as well.     

Recent transition metal catalysts for syndiotactic polystyrene

Syndiotactic polystyrene has attracted much interest in scientific and industrial research after its first synthesis in 1985 and has led to a fast commercialization of this polymer. The catalyst systems used for this coordination polymerization of styrene are a key point in this development to provide high polymerization activities and syndiotacticities of the polymers obtained.This literature review gives a comprehensive overview on the recent transition metal catalysts comprising the literature since about 2000 and especially on the transition metal complexes investigated in the syndiospecific homopolymerization of styrene. It includes the polymerization activity of the catalysts, the syndiotacticity of the polymers received as well as the discussion of the relationships between catalyst structure and polymerization activity. The complex-coordination mechanism of the syndiospecific polymerization of styrene is summarized in general at the beginning.The review of the recent transition metal catalysts for the syndiospecific styrene polymerization includes transition metal complexes, cocatalysts (methylaluminoxanes and boron compounds), activators and chain transfer agents, and supported and heterogenized catalysts. Transition metal complexes contain group 4 transition metal complexes (mono- and bis-cyclopentadienyl complexes, metal complexes of other ring systems such as indenyl, fluorenyl and other complexes, di- and multi-nuclear complexes, and non-metallocene complexes), and metal complexes of other transition metals (groups 8–10, rare earth metals, and others). The chapter on mono-cyclopentadienyl complexes demonstrates an overview on the investigations using unsubstituted cyclopentadienyl and pentamethylcyclopentadienyl complexes, on the influence of the variation of the structure of the cyclopentadienyl ligand, and on the effect of the variation of ancillary complex ligands besides cyclopentadienyl.This summary also considers recent developments in the preparation of new transition metal complexes based on the synthesis of completely novel π-ligands of the half-metallocenes, the success in attaining high syndiospecificities with transition metal complexes based on rare earth metals, the coordination polymerization in aqueous systems, the syndiospecific living polymerization, and new activators for the catalysts, with regard to syndiotactic polystyrenes.     

Gas sorption and transport in syndiotactic polystyrene with nanoporous crystalline phase

In this contribution we analyse sorption and transport of several gases in semicrystalline syndiotactic polystyrene with nanoporous crystalline δ form. Investigation was performed on amorphous samples and on samples characterized by different degrees of crystallinity. Sorption isotherms of carbon dioxide, nitrogen and oxygen in the crystalline phase have been determined starting from experimental results obtained for semicrystalline and amorphous samples. Corresponding isosteric heats of sorption were evaluated for the crystalline and amorphous phase. Permeation tests were also performed to gather information on mass transport properties of semicrystalline samples, evaluating average diffusivities of carbon dioxide and oxygen, in the limit of small concentrations as function of degree of crystallinity.     

Compatibilization effects of block copolymers in high density polyethylene/syndiotactic polystyrene blends

Three triblock copolymers of poly[styrene-b-(ethylene-co-butylene)-b-styrene] (SEBS) of different molecular weights and one diblock copolymer of poly[styrene-b-(ethylene-co-butylene)] (SEB) were used to compatibilize high density polyethylene/syndiotactic polystyrene (HDPE/sPS, 80/20) blend. Morphology observation showed that phase size of the dispersed sPS particles was significantly reduced on addition of all the four copolymers and the interfacial adhesion between the two phases was dramatically enhanced. Tensile strength of the blends increased at lower copolymer content but decreased with increasing copolymer content. The elongation at break of the blends improved and sharply increased with increments of the copolymers. Drop in modulus of the blend was observed on addition of the rubbery copolymers. The mechanical performance of the modified blends is strikingly dependent not only on the interfacial activity of the copolymers but also on the mechanical properties of the copolymers, particularly at the high copolymer concentration. Addition of compatibilizers to HDPE/sPS blend resulted in a significant reduction in crystallinity of both HDPE and sPS. Measurements of Vicat softening temperature of the HDPE/sPS blends show that heat resistance of HDPE is greatly improved upon incorporation of 20 wt% sPS.     

Annihilation kinetics of color center in irradiated syndiotactic polystyrene at elevated temperatures

In situ absorbance of syndiotactic polystyrene (sPS) at elevated temperatures is investigated. The irradiation environments of air, vacuum and oxygen are considered. The decreasing loss in transmittance after irradiation follows the sequence: oxygen, air and vacuum. The UV cut-off and shoulder wavelengths of sPS irradiated in an air atmosphere are greater than those in vacuum. Two types of color centers are responsible for the reduction of transmittance in the irradiated specimen. They are annealable and permanent. A first order annihilation model is proposed to analyze the annealable color centers. The results show that the annealable color center of sPS irradiated in vacuum required to overcome less energy barrier to annihilate than that in air, but the permanent color centers in the former is less than those in the latter after annealing. No annealable color center is observed in sPS irradiated in an oxygen atmosphere. The EPR spectra and FTIR spectra were also studied to enhance the understanding of kinetics of color center.     

Crystallization and morphological features of syndiotactic polystyrene induced from glassy state

Spherulitic growth rates and microstructure of syndiotactic polystyrene (sPS) cold-crystallized isothermally at various temperatures, T_c (115–240 °C), have been investigated by small-angle light scattering (SALS), optical microscopy and transmission electron microscopy. The derived activation energy for sPS chain mobility at the crystal growing front is 5.4 kJ/mol, which is relatively lower than that of isotactic polystyrene, 6.5 kJ/mol. In addition, the Hv scattering invariant (Q_Hv) measured by SALS on the crystallized sPS samples displays a pronounced minimum at 150 °C. Despite a wide range of T_c used, however, the sample crystallinity estimated by Fourier transformation infrared spectroscopy remains unchanged. Prior to crystallization, the correlation length derived from the Vv patterns on the basis of Debye–Bueche model is ca. 1.13 μm regardless of T_c used. Interconnected domains with a width of ca. 1.8±0.5 μm are readily observed in all the crystallized samples under phase contrast microscopy and the phase-separated structure is conserved within sPS spherulites whose diameters are increased with increasing T_c.

Based on the above facts, we conclude that the presence of a Q_Hv minimum is ascribed to the resultant events of the two competitive transitions i.e. liquid–solid crystallization, and liquid–liquid demixing resulting from the spinodal decomposition (SD). At lower T_c, the unstable SD transition overwhelms the crystallization. Despite the low chain mobility, the coarsening process driven by the interfacial energies has reached a certain level before crystalline nucleation takes place. At higher T_c, on the other hand, cold crystallization becomes the dominant process due to the enhanced chain mobility, leading to the suppression of ongoing SD coarsening process. At an intermediate T_c range, comparable competition of the phase separation and crystallization prohibits the development of ordered symmetry within spherulites, giving the presence of Q_Hv minimum.     

Analyses of crystal forms in syndiotactic polystyrene intercalated with layered nano-clays

A mixed polymorphic morphology of intercalated/exfoliated structure was observed in syndiotactic polystyrene (sPS)/clay nano-composites, which were successfully prepared by solution intercalation technique using 1,1,2,2-tetrachloroethane (TCE) as a solvent. Furthermore, X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses were used to examine the effect of montmorillonite clays (MMT, in pristine or organo-modified forms) in isothermally melt-crystallized sPS at several available crystallization temperatures (T_c) in a competitive environment of coexisting α- and β-crystals. A significant change in polymorphism of sPS was observed by the inclusion of different clays and the temperature regime of the α-crystal formation in sPS was found to increase considerably up to 250 °C by the presence of the organo-clay. Pristine clay (Na-MMT) was found to induce the β-crystal of sPS at all T_c's studied in this work. The overall thermodynamics of crystallization remained unchanged as the β-phases were found in major proportion at higher temperature of crystallization (∼260 °C), irrespective of the nature of the clays. The dispersibility of the clays in sPS matrix is assumed to play the pivotal role in modifying the crystalline structures, which was further corroborated by the polarized optical microscopy (POM). The spherulitic morphology clearly indicates differences in crystallites as affected by the nano-clays. Incorporation of organo-clay with nanoscale dispersibility through the intercalation of sPS molecules into the clay galleries was found to promote rapid formation of α-forms, which develops into spherulites of smaller dimension as compared to those of the β-forms. The alteration in melting behavior of sPS is attributed to the different crystallite structures that lead to formation of different kind of spherulites.