Isotactic Chains Research Articles

Details of the intermolecular interactions in poly(vinyl alcohol)-iodine complexes as studied by quantum chemical calculations

Abstract The electronic state of poly(vinyl alcohol) (PVA)-I 3 − ion complex has been successfully described for the first time on the basis of the density functional theoretical (DFT) calculations. (1) As the first trial, complex structure models between a short PVA chain (5-mer) and I 3 − ion were constructed, which were geometrically optimized and the energy change during the complexation was analyzed. Mainly the interaction between OH groups of PVA and iodine has been found to determine the stability of the complex. The interaction strength depends on the stereoregularity of the chain: the syndiotactic PVA sequence gave the strongest interactions between I 3 − and four or five OH sequence along the chain axis, while the atactic and isotactic chain models are less stable than the former case. The calculated interaction energy between PVA and I 3 − species was 36.0, 31.2 and 25.6 kcal/mol for syndiotactic , atactic and isotactic PVA, respectively. The calculation of orbital interactions revealed that the highest occupied molecular orbital (HOMO) of I 3 − is relatively close to the lowest unoccupied MO (LUMO) of PVA, causing an electron transfer from I 3 − to PVA. (2) In the second-stage calculation, the crystal structure model of PVA-iodine complex including counter ions (K + ) was built up by referring to the X-ray analyzed structure. The K + ions were found to be localized in the highly-negatively-charged space surrounded by OH groups and iodine atoms, corresponding well to the electrostatic potential minimum created by the PVA chains and iodine ions. The local molecular orbitals (LMO) calculated for these two models [(1) and (2)] revealed the existence of H-bonding interaction between the OH group and the iodine ion.

DSC study of silicas with immobilized polysiloxane layer of different architecture

Core–shell structured nanocomposites of polydimethylsiloxane with different polymerization degree (PMS100 and PMS50) and polymethylphenylsiloxane (PMPS4) immobilized onto fumed silica nanoparticles were studied by means of differential scanning calorimetry. The polysiloxanes were attached to the particles’ surface using thermally stimulated binding and modification in the presence of depolymerization activator—dimethyl carbonate (DMC). Single- and multi-stage processes were applied in order to obtain a different architecture of polymeric layer on the silica nanoparticles surface. The effect of polysiloxane/DMC ratio on phase transitions of obtained polymeric layers was evaluated. The grafting of polydimethylsiloxane at the presence of chain scissor resulted in cross-linking of the attached polymeric layers. When using a multi-step modification with PMPS, a dense cross-linked layer was formed on the silica surface. Unlike the samples obtained by one-step modification with different polymer content, for which the amount of polymer attached to silica surface changes the parameters of the relaxation process in polymeric layer, for composites synthesized using multi-stage modification, a greater influence has the length of the oligomer introduced on first stage. The best results were achieved for composite with PMPS when using on the first stage of modification the PMPS/DMC mixture with low content of depolymerization agent (oligomers with long chain, respectively). A notable increase in the mobility of the polymeric layer was detected due to the formation of isotactic macromolecular chains.

Local Structure Contributions to Surface Tension of a Stereoregular Polymer.

We have used all-atom molecular dynamics (MD) simulations to calculate the surface tension of melt poly(methyl methacrylate) (PMMA) as a function of tacticity. Computation of surface tension using the Kirkwood-Buff approach required hundreds of nanoseconds of equilibration. The computed slopes of surface tension versus temperature are in very good agreement with reported experimental values. Using a rigorous treatment of the true interface, which takes into account the molecular roughness, we find that isotactic PMMA, in comparison to syndiotactic and atactic PMMA, shows a larger surface concentration of polar ester-methyl and carbonyl groups on the surface versus nonpolar α-methyl groups. A mechanistic hypothesis based on the helical nature of the isotactic PMMA chains, their relative flexibility, and their reported conformational energies is proposed to explain the trends in composition near the surface. We highlight here how surface composition and surface tension are controlled by both polarity and steric constraints imposed by tacticity.

Tacticity effects on conformational structure and hydration of poly-(methacrylic acid) in aqueous solutions-a molecular dynamics simulation study

The influence of tacticity on chain dimensions, backbone and side-group conformational states and relaxation dynamics, intermolecular hydrogen bonding and its relaxation dynamics was investigated for 30 repeat unit poly(methacrylic acid) (PMA) as a function of the degree-of-neutralisation, f (i.e. charge density) [0 < f < 1 range] in explicit water with Na+ neutralising counter-ions, using molecular dynamics simulations. Chain expansion with increase in charge density is observed. Simulation results, where applicable, compare well with experimental results in the literature. Isotactic (i-PMA) chain exhibits the largest expansion (89% change in Rg), and syndiotactic (s-PMA-RR-0.7) chain shows 31%. For fully neutralised chain (high charge density), the probability for trans conformation at backbone bonds follows the trend i-PMA > a-PMA > s-PMA. At high charge density, a higher probability of trans state is obtained at meso dyads as compared to racemic dyads and the side group in i-PMA relative to other tacticity is conformationally more extended. RR triads impart better hydrogen bonding with water. In the COOH side group, greater rotational mobility is observed for i-PMA as compared to s-PMA. Water coordination to PMA is invariant with tacticity at low f. For f = 1, s-PMA exhibits the best level of H-bonding, due to its 3D chemical structural configuration. Binding distance between water and PMA atoms and their coordination number remain unchanged with respect to ionisation of COOH groups. Isotactic (i-PMA) exhibits the fastest relaxation of polymer-water H-bonds. While counter-ion coordination on to PMA is unaffected by tacticity, the intensity of ion condensation as well as hydrogen bond relaxation time at f = 1 varies in the order i-PMA > a-PMA > s-PMA.

Competition between α and β Crystallization in Isotactic Polypropylene: Effect of Nucleating Agents Composition

Abstract Based on the different nucleation ability, different contents and proportions of the mixed nucleating agents were melt compounded with pure isotactic polypropylene resins employed in this work, selective β nucleating agent was a compound of pimelic acid and calcium stearate, the α nucleating agent was a type of dibenzylidene sorbitol derivative. The competition attributed to the different type of interactions between a nucleating agent and isotactic polypropylene molecular chains during crystallization was investigated in this research. For a low content of the mixed nucleating agents used, α nucleation dominated the crystallization behavior of isotactic polypropylene, while with an increase of the content of the mixed nucleating agents, the situation was reversed and β nucleation became dominant. In the β dominated region, both of the molecular chain and segmental motions were various with different nucleating agent proportion. Thus, the content and proportion of the components of the nucleating agents were the critical factors in the competition during crystallization.

Effect of the composition of methanol−water mixtures on tacticity of poly(N‐ethylacrylamide) gel

ABSTRACTTwo series of macroporous poly(N‐ethylacrylamide) (PNEAM) gels are synthesized in different composition of methanol–water mixtures (xm = 0, 0.06, 0.13, 0.21, 0.31, and 0.43; where xm = mole fraction of methanol) in presence as well as in the absence of 0.1M Y(OTf)3 Lewis acid as additive. The gels synthesized in the absence of Lewis acid are atactic and in the presence of the same are isotactic. Synthesis of the corresponding linear PNEAM homopolymers shows that, the isotacticity (meso dyad, %) of the resulted polymers increases for the gels prepared in the presence of Lewis acid (LA) and remains constant for the gel prepared in the absence of LA, respectively, with the increase in the concentration of the synthesis solvent methanol. SEM micrographs reveal that, the hydrogels synthesized in the presence of LA are more porous than the gels prepared in the absence of LA. Swelling ratio of all the hydrogels decreases with the increase in the temperature and LA gels show higher swelling ratio values than non LA gels (NLA). Deswelling rate of the hydrogels prepared in methanol–water mixture in presence of LA is faster than the hydrogels prepared in absence of LA. Moreover, reswelling rate increases with increase in the isotacticity of the PNEAM segment in the gel. All these results have been explained on the basis of the formation of highly porous hydrogels with higher isotactic PNEAM chain segment in the presence of LA in methanol–water mixtures. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41668.

Synthesis and characterization of stereoregular poly(N-ethylacrylamide) hydrogel by using Y(OTf)3 Lewis acid

Macroporous poly(N-ethylacrylamide) (PNEAM) hydrogels have been prepared in a methanol-water (1:1, v/v) mixture in the presence of 0, 0.05, 0.1, 0.15, and 0.2 M yttrium trifluoromethanesulfonate [Y(OTf)3] Lewis acid (LA) concentrations. SEM micrographs show that the resulted hydrogels are highly porous. Swelling ratios of all the hydrogels in water decrease with the increase in the temperature, and the hydrogels show lower critical solution temperature (LCST) volume phase transition at around 75 °C. LCST of PNEAM homopolymers gradually increases with the increase in the isotacticity of the polymers. Moreover, the hydrogels show cononsolvency in different methanol-water mixtures at 50 °C. Deswelling rate of the hydrogels prepared in the presence of LA is higher than the gel prepared in the absence of LA and this rate increases with increase in the LA concentration. The reswelling rate of the hydrogels also follows the same order, that is reswelling rate also increases with the increase in the LA loading in the gels. All these results are explained on the basis of the formation of the highly porous hydrogels with a higher isotactic PNEAM chain segment in a methanol-water mixture in the presence of LA.

Improving microisotacticity of Ziegler–Natta catalyzed polypropylene by using triethylaluminum/triisobutylaluminum mixtures as cocatalyst

Propylene was polymerized with TiCl4/Di/MgCl2 catalyst and cocatalysts containing triethylaluminum (TEA) and triisobutylaluminum (TiBA) in the presence of Ph2Si(OMe)2 (external donor) and hydrogen. Chain structure of the formed polypropylene (PP) was characterized by temperature-rise elution fractionation (TREF) combined with DSC and 13C NMR analysis of the main fractions. Increasing the amount of TiBA in cocatalyst leads to decrease of isotactic index of PP, meanwhile the microisotacticity of the main TREF fractions of PP was enhanced. PP produced with the catalyst activated by a 50/50 TEA/TiBA mixture has the same content of highly isotactic chains as PP produced with the TEA activated catalyst, but main TREF fractions of the former has higher microisotacticity than the later. Fast alkyl exchanges in TEA/TiBA mixtures are found by 1H NMR analysis of the mixtures. By analyzing alkanes released from hydrolyzed catalysts that have been treated with the cocatalyst, alkylation power of TEA/TiBA mixture was found to decrease with increasing its TiBA content. The effects of TEA/TiBA mixture in propylene polymerization is explained by the weaker alkylation power and lower Lewis acidity of the mixed alkylaluminums than pure TEA. Decrease in the alkylation power leads to reduction of active centers with the highest stereospecificity, meanwhile decrease in Lewis acidity intensified the role of De in enhancing stereospecificity of different active centers. When the amount of TiBA in TEA/TiBA mixture falls in a suitable range, the later effect becomes dominant, and evident improvement in microisotacticity of PP can be achieved.

Microgel-like aggregates of isotactic and atactic poly(methacrylic acid) chains in aqueous alkali chloride solutions as evidenced by light scattering.

A comparative light-scattering study of isotactic and atactic poly(methacrylic acid), iPMA and aPMA, respectively, in aqueous solutions with added alkali chlorides, XCl (X = Li, Na, Cs), at 25 °C and XCl concentration of 0.1 mol L(-1), demonstrates that both PMA isomers are strongly associated at low degrees of neutralization, αN (= 0 for aPMA and 0.25 for iPMA), in the presence of all XCls. The shape parameter ρ and the scattering functions suggest that aggregates have the characteristics of microgel particles, with a dense core surrounded by a less dense shell. The extent of aggregation depends on the stereoregular structure of the polymer and on the type of the added cation. Li(+) and Na(+) ions support aggregation better than Cs(+) ions. Besides, iPMA chains are more strongly aggregated than aPMA chains and form particles with a denser core. A model of the aggregation process is suggested for iPMA. At high αN, a slow diffusive process (so-called extraordinary or anomalous mode in diffusion of polyelectrolytes), arising from electrostatic interactions between charged chains, is observed for both PMAs. Results suggest that under the same experimental conditions iPMA is effectively more charged than aPMA. The role of ions in the slow-mode phenomenon is less pronounced than in aggregation.

Effect of stereochemical sequence on the dynamics of atactic polypropylene melt

Dynamic Monte Carlo (DMC) simulation was used to study the dynamics of a series of coarse-grained atactic polypropylene (aPP) model chains (C192H578) in the melt state at 473 K. Model chains with meso diads factions, P m , set at 0.25, 0.5, and 0.75 but with different meso and racemo diads sequences were studied. It was observed that aPP chains with an alternate meso and racemo diads sequence exhibited the highest mobility (or diffusivity) among all stereochemical sequences studied. Additionally, chains with long consecutive sequences of diads of the same type exhibited lower mobility than those with more random stereochemical sequences. The differences in the intramolecular and intermolecular interactions resulting from differences in diad sequences contributed to the observed differences in dynamics. In particular, intramolecular interactions play a more dominant role for aPP chains containing low fractions of meso diads or none at all (i.e., all racemo diads (P m =0.0) or syndiotactic chains). On the other hand, in the cases of P m values close to 1.0 (i.e., isotactic chains), intermolecular interactions play a more dominant role than the intramolecular interactions.

Understanding the Interaction between Trivalent Lanthanide Ions and Stereoregular Polymethacrylates through Luminescence, Binding Isotherms, NMR, and Interaction with Cetylpyridinium Chloride

Complexation of isotactic, syndiotactic, and atactic poly(methacrylic acid), PMA, with trivalent lanthanide ions has been studied in water at a degree of neutralization 0.5. Metal ion binding is shown by quenching of cerium(III) fluorescence, enhancement of Tb(III) luminescence, and lanthanide-induced line broadening in the PMA (1)H NMR spectra. Comparison with lanthanide-acetate complexation suggests carboxylate binds in a bidentate fashion, while Ce(III) luminescence quenching suggests an ≈3:1 carboxylate:metal ion stoichiometry, corresponding to charge neutralization. The presence of both free and bound Ce(III) cations in PMA solutions is confirmed from luminescence decays. Studies of Tb(3+) luminescence lifetime in H2O and D2O solutions show complexation is accompanied by loss of 5-6 water molecules, indicating that each bidentate carboxylate replaces two coordinated water molecules. The behavior depends on pH and polyelectrolyte stereoregularity, and stronger binding is observed with isotactic polyelectrolyte. Binding of cetylpyridinium chloride, CPC, in these systems is studied by luminescence, NMR, and potentiometry. NMR and Tb(3+) luminescence lifetime studies show the strongest binding with the isotactic polymer. Binding of surfactant to poly(methacrylate) in the presence of lanthanides is noncooperative, i.e., it binds to the free sites; binding isotherms in the presence of lanthanides are shifted to higher free surfactant concentrations, compared with sodium ions, have lower slopes and show a clear two-step binding mechanism. While CPC readily replaces the Na(+) ions of poly(methacrylate) and binds very strongly (low critical association concentrations), exchange is much more difficult with the strongly bound trivalent lanthanide ions. Effects of tacticity are seen, with surfactant interacting most strongly with isotactic chains in the initial stages of binding, while in the final stages of binding the interaction is strongest with atactic poly(methacrylate).

Polymers of propylene and higher 1-alkenes produced with post-metallocene complexes containing a saligenin-type ligand

Polymerization reactions of propylene and three higher linear 1-alkenes, 1-hexene, 1-octene and 1-decene, were carried out with post-metallocene catalysts derived from Ti complexes I and II with a bidentate phenol-alcohol (saligenin-type) ligand derived from 2,4-di-tert-butyl-6-(1,1,1,3,3,3-hexafluoro-2-hydroxy-propan-2-yl)phenol, in the presence of two cocatalysts, MAO and a combination of AlEt2Cl and MgBu2. All catalyst systems contain a large variety of active centers and produce both amorphous atactic polymers and partially crystalline isotactic material. The AlEt2Cl-MgBu2 cocatalyst produces significantly more active catalyst systems. Analysis of 13C NMR data for the propylene polymers shows that the mechanism of isotactic chain growth is principally different for the active centers formed in the presence of the two cocatalysts.

Probing the roles of diethylaluminum chloride in propylene polymerization with MgCl2-supported ziegler-natta catalysts

In this article, the effect of diethylaluminum chloride (DEAC) in propylene polymerization with MgCl2-supported Ziegler-Natta catalyst was studied. Addition of DEAC in the catalyst system caused evident change in catalytic activity and polymer chain structure. The activity decrease in raising DEAC/Ti molar ratio from 0 to 2 is a result of depressed production of isotactic polypropylene chains. The number of active centers in fractions of each polymer sample was determined by quenching the polymerization with 2-thiophenecarbonyl chloride and fractionating the polymer into isotactic, mediumisotactic and atactic fractions. The number of active centers in isotactic fraction ([Ci*]/[Ti]) was lowered by increasing DEAC/Ti molar ratio to 2, but further increasing the DEAC/Ti molar ratio to 20 caused marked increase of [Ci*]/[Ti]. The number of active centers that produce atactic and medium-isotactic PP chains was less influenced by DEAC in the range of DEAC/Ti = 0–10, but increased when the DEAC/Ti molar ratio was further raised to 20. The propagation rate constant of Ci* (k pi) was evidently increased when DEAC/Ti molar ratio was raised from 0 to 5, but further increase in DEAC/Ti ratio caused gradual decrease in k pi. The complicated effect of DEAC on the polymerization kinetics, catalysis behaviors and polymer structure can be reasonably explained by adsorption of DEAC on the central metal of the active centers or on Mg atoms adjacent to the central metal.

Linear and star‐shaped POSS hybrid materials containing crystalline isotactic polystyrene chains

AbstractNew crystalline nanostructured inorganic–organic hybrid materials containing isotactic polystyrene (iPS) are prepared by means of hydrosilylation coupling of vinyl‐terminated iPS with octakis(dimethylsilyloxy)silsesquioxane (Q8M8H). The number average molar mass of the iPS chains varies between 2000 and 6000 g mol−1. As a function of the iPS/Q8M8H ratio, using excess reagent, the formation of linear or star‐shaped hybrid architectures is achieved. Via fractionation, it is possible to isolate well‐defined linear hybrids containing one iPS chain and seven ethyl groups per silica core (iPS‐Q8M8E7) as well as star‐shaped hybrids containing up to eight iPS side chains (iPS6‐8‐Q8M8). These new iPS/polyhedral oligomeric silsesquioxane hybrid materials crystallize when the number average molar mass of iPS side chain exceeds 5500 g mol−1. The hydrosilylation coupling reaction and the resulting linear iPS‐Q8M8E7 and star‐shaped iPS6‐8‐Q8M8 are characterized by NMR spectroscopy, size exclusion chromatography (gel permeation chromatography), and polarized light microscopy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

Colloidal Analogues of Charged and Uncharged Polymer Chains with Tunable Stiffness

Herein, we describe new methods to produce colloidal particle chains of three stiffness regimes that can be observed on a single-particle level, that is, on the level of the monomers that make up the chain; the chains can even be observed in concentrated systems without using molecular tracers. These methods rely on the following: dipolar interactions induced by external electric fields in combination with long-range charge repulsion to assemble the particles into chains only, and a bonding step to ensure that the particles remain assembled as chains even after the external field is switched off. We can control the length and the flexibility of the chains. Additionally, we demonstrate that our method is generally applicable by using it to prepare several other colloidal polymers, such as block-copolymer chains, which are formed by combining rigid and flexible chains, spherocylinders, which are formed by heating rigid chains, and both atactic and isotactic chains, which are formed from heterodimericparticle monomer units. We demonstrate that the flexibility of the charged chains can be tuned from very rigid (rod-like) to semiflexible (as in the simplified polymer model of beads on a string) by changing the ionic strength. This method can, in principle, be used with any type of colloidal particle. Moreover, our systems can be matched in terms of refractive index and density, so that bulk measurements in real space are possible.

Raman structural study of random copolymers of propylene with 1-pentene

Nascent form of random propylene/1-pentene copolymers was studied for the first time by Raman spectroscopy. For the purpose of detailed interpretation of the copolymer spectra, we investigated Raman spectra of neat PP with low and high crystallinity. It was found that the copolymer Raman spectra depend on the 1-pentene content. We registered the most significant spectral alterations in two lines at 809 and 841 cm−1. The first line corresponds to vibrations of polypropylene (PP) isotactic chains in the crystalline phase, while the second one is associated with vibrations of PP isotactic chains having isomeric defects. We found out that increase in the 1-pentene content results in reduction of the copolymer crystallinity and in the content of isotactic chains in the copolymer amorphous phase.

PLA–PEG copolymers micronization by supercritical assisted atomization

Supercritical assisted atomization (SAA) under reduced pressure was used to produce microparticles with defined spherical morphology, controlled particle size and distribution of PEG–PLA copolymers. These compounds, because of their low glass transition temperature are difficult to process using other techniques.Different architectures were tested to optimize PEG–PLA copolymers from the point of view of SAA processability and their pharmaceutical application. Synthesis and micronization of copolymers with relative content of PEG:PLA of 1:4 (w/w) and 1:8 (w/w) and with atactic or stereoregular (isotactic) PLA arms were performed and the architectures of linear copolymers (l, PEG(PLA)), branched of first generation (G1, PEG(PLA)2) and branched of second generation (G2, PEG(PLA)4), characterized by one, two and four PLA arms respectively, were tested.Well defined particles of the linear copolymer PEG–PLA, with isotactic PLA chain, were obtained with a mean particle size of 0.25–0.45μm, for both PEG:PLA ratios. G2 branched copolymer were successfully micronized in the case of 1:8 PEG:PLA ratio with isotactic PLA blocks and spherical particles with a mean particle size of about 0.3μm were obtained. On the contrary, the G1 copolymers with isotactic PLA arms formed coalescing microparticles when processed by SAA. Copolymers with atactic PLA arms, independently on the architecture, were not successfully processable.SAA process did not modify the structure of the starting copolymers, as shown by 1H NMR and GPC analyses. The microparticles obtained showed a lower degree of crystallinity compared to the untreated materials, as confirmed by XRPD and DSC analyses. The G2 branched 1:8 PEG:PLA copolymer, because of the structure and the size of the obtained particles, can be considered the most promising for the controlled release of a drug.

具有极性大侧基乙烯基聚合物的分子尺寸和均方二极矩

The formulas of basic quantities, mean-square radius of gyration and mean-square dipole moment, are re-deduced by the rotational-isomeric-state model and the generator matrix method with considering large side groups of polymers. From investigation for the configuration-conformation dependent properties of poly( N -vinylcarbazole) (PVK), poly( p -chlorostryere) (PPCS), poly(2-vinyl pyridine) (P2VP) and poly(vinyl pyrrolidone) (PVP), the characteristic ratios of mean-square dipole moment are obtained 0.55, 0.57, 0.48 and 0.37, respectively, and the ratios of mean-square radius of gyration are 2.07, 1.74, 1.11 and 1.52, respectively. The temperature coefficients of the isotactic chains, in range of -6.1×10 -3 ~ 2.1×10 -3 K -1 , are more than that of the syndiotactic chains and atactic chains. From comparing the constrained relation of the ratios, it is found that effect of polymerization degree of chains, the chain tacticity and conformational energies on the basic quantities of PPCS, PVP and P2VP are obvious relatively. Moreover, the larger side groups of PVK chain result in the greater characteristic differences between the mean-square dipole moment and mean-square radius of gyration. From contrasting the results of improved calculation, it is concluded that the consideration of orientation and dimension of dipolar side groups in calculation of mean-square dipole moment and radius of gyration are very significant. Therefore, it suggests that the effect of large dipolar side groups on the polarity and flexibility of polymers cannot be neglected.

Supported neodymium catalysts for MMA polymerization: on the origin of surface-induced stereoselectivity

The polymerization of MMA by a supported neodymium borohydride catalyst proceeds with moderate tendency toward isoselectivity, whereas the molecular precursor generates a syndiotactic-rich polymer. DFT studies reveal that initiation proceeds via borohydride attack on the first coordinated monomer followed by BH3 trapping by the silica surface. The selectivity of the next two insertions was scrutinized, demonstrating that interactions between the growing chain's oxygens and the metal enforce conformations that lead to favoured formation of an isotactic polymer chain.

Synthesis and crystallization behavior study of syndiotactic polystyrene-g -isotactic polypropylene (sPS-g -iPP) graft copolymers

Based on coordination polymerization mechanism only, novel stereoregular graft copolymers with syndiotactic polystyrene main chain and isotactic polypropylene side chain (sPS-g-iPP) were synthesized via two steps of catalytic reactions. First, a chain transfer reaction was initiated by a chain transfer complex composed of a styrene derivative, 1,2-bis(4-vinylphenyl)ethane, and hydrogen in propylene polymerization mediated by rac-Me2Si[2-Me-4-Ph(Ind)]2ZrCl2 and MAO, which gave iPP macromonomer bearing a terminal styryl group (iPP-t-St). Then the iPP-t-St macromonomers of varied molecular mass were engaged in syndiospecific styrene polymerization over a typical mono-titanocene catalyst (CpTiCl3/MAO) under different conditions to produce sPS-g-iPP graft copolymers of varied structure. With an effective purification process, well-defined sPS-g-iPP copolymers were obtained, which were then subjected to differential scanning calorimetry (DSC) and polarized optical micrograph (POM) studies. The graft copolymers were generally found with dual melting and crystallization temperatures, which were ascribable respectively to the sPS backbone and iPP graft. However, it was revealed that the two segments displayed largely different melting and crystallization behaviors than sPS homopolymer and the precursory iPP-t-St macromonomer. Consequently, the graft copolymer exhibited much distinctive crystalline morphologies when compared with their individual components. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.