Search Results (12)

Crystallization can be exploited as an architecture-forming step for polymer membranes because it builds a load-bearing semicrystalline scaffold while simultaneously defining amorphous regions that later become transport pathways. Herein, we quantify how thermal history programs isotactic polystyrene (iPS) crystallization and translate the resulting microstructures into membrane-relevant design rules. Lux-calibrated digitally extracted pixel intensity (DPI) from polarized optical microscopy provides a quantitative, spatially resolved crystallinity proxy; benchmarking against differential scanning calorimetry confirms that the DPI proxy exhibits the same onset, peak, and completion signatures under matched temperature programs. The DPI–DSC agreement yielded R² = 0.98 under matched programs. We compared crystallization initiated from molten and glassy states across a wide range of melt pretreatments and crystallization temperatures. Molten-state pathways display pronounced melt-memory behavior: modest changes in melt pretreatment shift induction time and half-time and drive textures from dense, fine spherulitic fields to sparse, coarser morphologies. In contrast, glassy-state crystallization largely suppresses melt history, yielding overlapping sigmoidal crystallinity curves and stable kinetic parameters consistent with relaxation-mediated nucleation. Avrami analyses indicate three-dimensional growth in both routes but highlight the strong melt-history sensitivity of apparent rate constants in the molten state. The crystallization rate and half-life show bell-shaped temperature dependence. Finally, saturated nucleation density correlates with the melting response, providing a practical link between kinetic observables and morphology. The processing–morphology map provides membrane-relevant design rules by linking thermal history to nucleation density and scaffold texture, which are expected to influence transport and mechanical stability in downstream membrane fabrication. In this study, “membrane architecture” is used in a pre-fabrication sense to denote the crystallization-programmed semicrystalline scaffold expected to govern subsequent pore-generation behavior and mechanical stability. Accordingly, the present work establishes a quantitative process–structure map for iPS scaffold design. Full article

The concept of a circular economy, where waste materials are transformed into valuable resources, is gaining increasing attention. However, many waste streams are difficult to recycle due to their mixed composition and broad molecular distribution. This paper explores the potential of repurposing mixed materials, specifically focusing on creating a circular alternative to bitumen, a fossil-based binder used in road construction. The molecular weight and composition of bitumen are analyzed using gas chromatography (GC) and infrared spectroscopy (IR). This study proposes using waste plastics and bio-based oils to develop a paving binder with similar molecular distribution. Various plastic types, such as low-density polyethylene (LDPE), high-density polyethylene (HDPE), isotactic polypropylene (PP), polystyrene (PS) and polyethylene terephthalate (PET), are examined for their compatibility with different oils. It is observed that the compatibility of both the molecular weight and composition between the plastic and oil is crucial for the successful dissolution and homogeneity of the binder. Additionally, the crystallinity of the plastic plays a role in the flexibility and durability of the resulting binder. It is demonstrated that by carefully selecting waste materials and understanding their molecular characteristics, it is possible to create circular alternatives to fossil-based materials like bitumen. This approach has the potential to reduce waste, lower dependence on fossil resources, and contribute to sustainable and circular construction materials. Full article

The existing phase field model of polymer crystallization contains many parameters that lack actual physical meaning. Although the value of these parameters can be adjusted to obtain results consistent with the experiment, it cannot correspond to the experimental conditions. In this paper, a new phase field model is established. By adjusting the latent heat, various forms of isotactic polystyrene crystals, such as dendrites, spherulites, lamellas, etc., can be simulated. Latent heat refers to the heat absorbed or released by a substance from one phase to another and has important physical meaning during the solidification process. The finite difference method was used to solve the model, and then the data were used to visualize. The simulation results were consistent with the experiment. Numerical simulation results under pure diffusion conditions show that the newly established phase field model can qualitatively predict the polymer growth process and provide a theoretical basis for the preparation and optimization of high-performance polymers. In order to make the simulation result closer to the actual growth of the crystal, the flow velocity is added in the simulation to make the melt convection. Under forced convection, the simulated polymer crystal image is no longer symmetrical. Full article

In this work, a series of isotactic-polypropylene/atactic-polystyrene (iPP/aPS) miktoarm star copolymers, P_xS_y, was synthesized via an arm-first approach. Varied star macromolecule architectures were fabricated by designing the arm length and the arm numbers (x and y). These miktoarm stars were able to form micelles in selective solvent (N,N′-dimethylformamide (DMF)), in which the insoluble iPP arms formed the core and the soluble aPS arms formed the shell. The miktoarm polymers aggregated to micro-nanoscale binary structures (MNBSes) in the casting process, and their morphologies, including the MNBS shape and size, were greatly influenced by the P_xS_y architectures. The MNBSes endowed the material surface with superhydrophobic performance with a water contact angle of 157.0° and a sliding angle of 1.5°. Full article

The dibenzyl zirconium(IV) complex (4) incorporating with a carbazolyl(Cbz)-substituted [OSSO]-type bis(phenolate) ligand was synthesized. Upon activation with dried modified methylaluminoxane (dMMAO), precatalyst 4 at relatively low catalyst loadings was found to promote the 1,2-regioselective oligomerization of 1-hexene to produce the corresponding vinylidene-ended oligomers with moderate turnover frequencies (TOFs) up to 2080 h⁻¹. The ¹³C NMR analysis of the resulting oligomers revealed the formation of dimer-enriched oligo(1-hexene)s in 39–62% distributions. The precatalyst 4 with dried methylaluminoxane (dMAO) also exhibited good performance in the polymerization of styrene yielding isotactic polystyrenes ([mm] > 99%) with quite large molecular weights (M_w < 508,100 g mol⁻¹) and relatively high catalytic activity (up to 2810 g mmol(4)⁻¹ h⁻¹). Full article

Nano-sized one-dimensional metallo-organic polymers, characterized by the phenomenon of spin transition, are excellent candidates for advanced technological applications such as optical sensors, storage, and information processing devices. However, the main drawback of this type of polymers is their fragile mechanical properties, which hinders its processing and handling, and makes their practical use unfeasible. To overcome this problem, in this work, hybrid thermo-reversible gels are synthesized by combination of a metallo-organic polymer and isotactic polystyrene (iPS) in cis-decaline. A detailed investigation of the thermal and viscoelastic properties of the hybrid gels, in terms of iPS and metallo-organic polymer concentration is performed by means of differential scanning calorimetry and oscillatory rheology, respectively. From the analysis of the thermal properties, three transitions have been determined upon heating: Monotectic transition of the iPS gel, melting of the iPS gel, and melting of the metal-organic polymer gel, which suggest that the gels of the two polymers are formed independently in the hybrid gel, as long as the two polymers are in concentrations above the corresponding critical gelation concentrations. Results regarding viscoelastic properties and morphology confirmed that hybrid gels consisted of an interpenetrated network of polymer gels, formed by iPS and metallo-organic poymer gels growing independently. Full article

In recent years, the synthesis of novel organic molecules that spontaneously self-assemble into a large variety of molecular architecture, particularly the formation of organogels, has yielded new opportunities in the preparation of functional materials. Here, we present an original preparation path of such materials through the fabrication of hybrid gels of these molecules with covalent polymers. Three types of systems are described: (i) intermingled gels where a polymer gel and an organogel pervade one another; (ii) encapsulation of self-assembled filaments in polymer fibrils, which provides a system with unusual magnetic properties; (iii) the reverse situation in which self-assembled nanotubes sheathe polymer fibrils. Two covalent polymers are considered: a neutral polymer, specifically stereoregular polystyrene (isotactic or syndiotactic), and a semi-conducting polymer, P3BT. In the latter case, semi-conducting nanowires are obtained. Full article

A multi-scale phase-field approach, which couples the mesoscopic crystallization with the microscopic orientation of chain segments and macroscopic viscoelastic melt flow, is proposed to study how the crystal growth of semi-crystalline polymers is affected by flows. To make the simulation feasible, we divide the problem into three parts. In the first part, a finitely extensible nonlinear elastic (FENE) dumbbell model is used to simulate the flow induced molecular structure. In the second part, formulas for estimating the density, orientation and aspect ratio of nuclei upon the oriented molecular structure are derived. Finally, in the third part, a massive mathematical model that couples the phase-field, temperature field, flow field and orientation field is established to model the crystal growth with melt flow. Two-dimensional simulations are carried out for predicting the flow effect on the crystal growth of isotactic polystyrene under a plane Poiseuille flow. In solving the model, a semi-analytical method is adopted to avoid the numerical difficult of a “high Weissenberg number problem” in the first part, and an efficient fractional step method is used to reduce the computing complexity in the third part. The simulation results demonstrate that flow strongly affects the morphology of single crystal but does not bring a significant influence on the holistic morphology of bulk crystallization. Full article

The three equations involved in the time-temperature superposition (TTS) of a polymer, i.e., Williams–Landel–Ferry (WLF), Vogel–Fulcher–Tammann–Hesse (VFTH) and the Arrhenius equation, were re-examined, and the mathematical equivalence of the WLF form to the Arrhenius form was revealed. As a result, a developed WLF (DWLF) equation was established to describe the temperature dependence of relaxation property for the polymer ranging from secondary relaxation to terminal flow, and its necessary criteria for universal application were proposed. TTS results of viscoelastic behavior for different polymers including isotactic polypropylene (iPP), high density polyethylene (HDPE), low density polyethylene (LDPE) and ethylene-propylene rubber (EPR) were well achieved by the DWLF equation at high temperatures. Through investigating the phase-separation behavior of poly(methyl methacrylate)/poly(styrene-co-maleic anhydride) (PMMA/SMA) and iPP/EPR blends, it was found that the DWLF equation can describe the phase separation behavior of the amorphous/amorphous blend well, while the nucleation process leads to a smaller shift factor for the crystalline/amorphous blend in the melting temperature region. Either the TTS of polystyrene (PS) and PMMA or the secondary relaxations of PMMA and polyvinyl chloride (PVC) confirmed that the Arrhenius equation can be valid only in the high temperature region and invalid in the vicinity of glass transition due to the strong dependence of apparent activation energy on temperature; while the DWLF equation can be employed in the whole temperature region including secondary relaxation and from glass transition to terminal relaxation. The theoretical explanation for the universal application of the DWLF equation was also revealed through discussing the influences of free volume and chemical structure on the activation energy of polymer relaxations. Full article

This contribution presents an updated overview of the different copolymers containing stereoregular polystyrene blocks. Special emphasis is placed on syndiospecific and isospecific copolymerization of styrene with co-monomers (ethylene and α-olefins, conjugated and non-conjugated dienes, styrene derivatives, etc.). The catalytic systems involved are described and the polymerization mechanisms are discussed. Alternative approaches (simultaneous, living, chain-transfer and graft copolymerization) and the resulting detailed structures and characteristics of the copolymers are also reported. Full article

Flow induced crystallization of semi-crystalline polymers is an important issue in polymer science and engineering because the changes in morphology strongly affect the properties of polymer materials. In this study, a phase field technique considering polymer characteristics was established for modeling and predicting the resulting morphologies. The considered crystallization process can be divided into two stages, which are nucleation upon the flow induced structures and subsequent crystal growth after the cessation of flow. Accordingly, the proposed technique consists of two parts which are a flow induced nucleation model based on the calculated information of molecular orientation and stretch, and a phase field crystal growth model upon the oriented nuclei. Two-dimensional simulations are carried out to predict the crystallization morphology of isotactic polystyrene under an injection molding process. The results of these simulations demonstrate that flow affects crystallization morphology mainly by producing oriented nuclei. Specifically, the typical skin-core structures along the thickness direction can be successfully predicted. More importantly, the results reveal that flow plays a dominant part in generating oriented crystal morphologies compared to other parameters, such as anisotropy strength, crystallization temperature, and physical noise. Full article

The article is focused on analyzing the effect of functionalization and reactive processing on the morphological, thermal, rheological and mechanical properties of composites of isotactic polypropylene (PP), polystyrene (PS), poly(ethylene-vinyl acetate) (EVA), with cellulose fibers, hemp or oat as natural fillers. Both polymers and fibers were modified with bi-functional monomers (glycidyl methacrylate, GMA; maleic anhydride, MA) capable of facilitating chemical reactions between the components during melt mixing. Polyolefin copolymers containing reactive groups (PP-g-GMA, SEBS-g-MA, PS-co-MA, etc.) were used as compatibilizers. Optical and SEM microscopy, FTIR, RX, DSC, TGA, DMTA, rheological and mechanical tests were employed for the composites characterization. The properties of binary and ternary systems have been analyzed as a function of both fiber and compatibilizer content. All compatibilized systems showed enhanced fiber dispersion and interfacial adhesion. The phase behavior and the thermal stability of the composites were affected by the chemical modification of the fibers. Marked changes in the overall crystallization processes and crystal morphology of PP composites were observed owing to the nucleating effect of the fibers. The tensile mechanical behavior of the compatibilized composites generally resulted in a higher stiffness, depending on the fiber amount and the structure and concentration of compatibilizer. Full article