Properties Of Crystalline Polymers Research Articles

Effect of N,N'-Dicyclohexyl Terephthalic Dihydrazide on the Crystallization and Properties of Isotactic Polypropylene

Application of nucleating agents is a common way to manipulate the structure and properties of crystalline polymers. Our goal was to synthesize N,N'-dicyclohexyl terephthalic dihydrazide (DCTDH) and study it from the viewpoint of applicability as a nucleating agent for isotactic polypropylene (iPP). We used differential scanning calorimetry to investigate the efficiency of DCTDH in samples containing the nucleating agent in a wide concentration range. We used polarized light microscopy to study the crystalline morphology developed in the presence of this nucleating agent. To characterize the mechanical properties of the nucleated samples, we performed tensile and impact tests on injection molded specimens. DCTDH proved to be a non-soluble α-nucleating agent in iPP, with a saturation concentration around 300 ppm. The nucleating agent has a significant effect on the crystalline structure of iPP, microspherulitic structure forms in its presence. Owing to the different structure, a considerable change in the mechanical properties is observable: with increasing nucleating agent content the tensile modulus increases, while impact resistance has a maximum value around 300 ppm nucleating agent content.

Synergistic Engineering of Side Chains and Backbone Regioregularity of Polymer Acceptors for High‐Performance All‐Polymer Solar Cells with 15.1% Efficiency

AbstractTuning the aggregation and crystalline properties of polymers is critical for realizing all‐polymer solar cells (all‐PSCs) with optimal blend morphology and high power conversion efficiency (PCE). In this study, a series of polymerized small‐molecule acceptors (PSMAs) is developed to investigate important relationships among their crystalline/aggregation properties, the blend morphology, and the device performance of the resulting all‐PSCs. A series of PSMAs (regiorandom (RRd)‐C12, RRd‐C20, RRd‐C24, regioregular (RRg)‐C20, and RRg‐C24) with simultaneously‐engineered i) side chain lengths of C12, C20, and C24, and ii) backbone regioregularities of RRd and RRg are synthesized to regulate their crystalline/aggregation properties. As a result, the highest PCE of 15.12% is obtained with all‐PSCs based on RRg‐C20 PSMA having regioregular backbone and optimal side chain length, attributed to high PSMA crystallinity and electron mobility as well as optimal blend morphology with a polymer donor. Thus, this study demonstrates the importance of simultaneous engineering of the backbone regioregularity and side‐chain structures of PSMAs to enhance electron mobility, optimize blend morphology and, thus, achieve highly efficient all‐PSCs.

A combined numerical and experimental study for characterizing interfacial properties of polyoxymethylene–calcium carbonate nanocomposites in tensile state

In this research, experimental and numerical approaches used simultaneously to discover the mechanical properties of interphase region formed in polyoxymethylene (POM)/calcium carbonate (CaCO3) nanocomposites. For acquiring interphase thickness, differential scanning calorimetry thermo-analytical data were incorporated by assuming that the whole crystallization of polymer matrix developed only in the interphase region. An inverse mode of a micromechanical equation known as effective interface model was used to acquire the interphase stiffness tensor. To obtain tensile strength of interphase region, a parametric study was designed and proceeded using finite element analysis method. The formations of interphase regions in POM/CaCO3 nanocomposites, which had 25–85% higher modulus and 10–50% higher strength than matrix led to as high as 40% and 14% improvements in the nanocomposite Young’s modulus and tensile strength, respectively. The proposed method provides further accuracy in obtaining interphase properties of crystalline polymers reinforced by mineral nanoparticles.

Determining Optimal Crystallinity of Diketopyrrolopyrrole-Based Terpolymers for Highly Efficient Polymer Solar Cells and Transistors

A new series of conjugated random terpolymers (PDPP2T-Se-Th) was synthesized from an electron-deficient diketopyrrolopyrrole (DPP)-based unit in conjugation with two electron-rich selenophene (Se) and thiophene (Th) species, with a view to inducing different crystalline behaviors of the polymers. The crystallinity of the polymers can be systematically controlled by tuning the ratio between Se and Th; an increase in Se content induced a remarkable increase in the melting and crystallization temperatures as well as the crystallinity of the PDPP2T-Se-Th terpolymers. These changes in the crystalline properties of polymers had a dramatic effect on the performances of organic field-effect transistors (OFETs) and polymer solar cells (PSCs). However, their effect on each type of devices was very different. The charge carrier mobilities of the PDPP2T-Se-Th terpolymers in OFET devices increased remarkably as the Se content increased in the polymers, showing that PDPP2T-Se100 with Se/Th ratio = 100/0 had very high h...

PVT Properties of crystalline polymers. Comparison of Theoretical Predictions and Experimental Data

We compare theoretical predictions of the pVT properties of crystalline polymers with experimental data for polyethylene. We took into account the effect of temperature, lattice coordination number, number of coordination spheres, and other parameters on the volume of the polymer crystal. The experimental and theoretical data on the dependence of the volume of crystalline polyethylene at atmospheric pressure are quite consistent with each other.

Preparation of Conducting Liquid Crystalline Polymer Based of Poly(2-ethanol aniline)

The authors prepared a novel conducting liquid crystalline polymer based poly(2-ethanol aniline) by chemical and electrochemical methods. First, 2-anilinoethyl-3-chloropropionate was synthesized by reaction of 2-ethanol aniline and 3-chloropropionate in presence of dicyclohexylcarbodiimide (DCCI) and (dimethylamino)pyridine (DMAP). Then, {2-[ethyl[4-[(4-nitrophenyl)azo]phenyl]amino]ethanol}, Disperse Red-I, (Red1) was prepared from addition of 2-(N-ethyl-N-phenylamine) with the 4-nitrobenzenamine. Potassium salt Red1 was prepared by reaction of potassium and Red1 in THF. Then added to 2-anilinoethyl-3-chloropropionate for chemically synthesis of poly[2-anilino-{3-[2-[ethyl[4-[(4-nitrophenyl)azo]phenyl]amino] propanoate]}], Poly(2AECP-Red1). Produced polymer was characterized using FT-IR, UV-visible, and 1H, 13C-NMR spectroscopies. The thermal and liquid crystalline properties of polymer were studied by thermogravimetric and differential scanning calorimetry. Scanning electron microscopy images supported the formation of polymer and showed morphology feature and homogeneous structure on polymer. Electrical conductivity of Poly(2AECP-Red1) has been studied by four-point probe method and produced 4.9 × 10–3 S/cm conductivity for it.

Liquid crystalline H-bonded polymers influenced by chiral and achiral spacers

A new series of main chain H-bonded liquid crystalline polymers were derived from binary mixtures of mesomorphic polymer (I or II) and non-mesomorphic guest molecules like suberic acid, tartaric acid and alkylated tartaric acid. The role of flexible chiral (tartaric acid and alkylated tartaric acid) and achiral (suberic) guest molecules on mesomorphism has been studied. Liquid crystalline properties of polymers and its guest acid complexes were investigated by DSC and POM analysis. The isotropic and melting temperatures of the polymers have been drastically reduced by mixing with flexible guest molecules.

Miscibility of polyamide-6,6 with aromatic polyamides

The polyamides with aromatic rings in the main chain were synthesized by the solution polymerization of 4,4′-diphenylmethane diisocyanate and aliphatic dicarboxylic acid in the presence of catalyst. The thermal properties and the miscibility behaviours with polyamide-6,6 of these aromatic polyamides were studied. The aromatic polyamides synthesized with one kind of dicarboxylic acid had typical thermal properties of crystalline polymers, whereas those synthesized with the mixtures of dicarboxylic acids were not easily crystallized. The observed miscibility behaviours showed some differences from those predicted by binary interaction model.

結晶性高分子の微細構造と力学的性質 主として１次元配向材料―繊維材料について

結晶性高分子の微細構造と力学的性質 主として１次元配向材料―繊維材料について

The Relation between Structure and Properties of Crystalline Polymers

The influence of both structure and crystallization conditions on a variety of properties characteristic of semi-crystalline polymers are discussed. A careful distinction needs to be made between molecular structure and the independent structural variables which describe the crystalline state. This set of independent variables includes the degree of crystallinity; the structure of the non-crystalline regions; the crystallite thickness distribution; the structure and relative amount of interface; the crystallite structure and the supermolecular structure. The dependence of these variables on molecular structure and crystallization conditions are examined in detail as is their influence on properties. By following this procedure the influence of molecular structure on properties is deduced. A variety of thermodynamic, spectral and mechanical properties are analyzed by these methods.

Effect of hydrostatic pressure on mechanical properties of crystalline polymers under shear

1. Superimposing hydrostatic pressure increases shear strain resistance and leads to a reduction in structural defects. 2. A sharp reduction in shear modulus and yield point at 50–60 °C caused by superimposing hydrostatic pressure is explained by the presence of a relaxation transition at this temperature and is the result of freezing the amorphous phase of the partially recrystallized polymer by the action of pressure. 3. A uniform change in elasticity modulus and yield point with increasing pressure was established in the temperature ranges not containing relaxation transitions. 4. Limits were established for external parameters at which shear diagram similarity is observed.

Structure and properties of crystalline polymers

Recent advances and status of x-ray structure analysis of crystalline polymers are described using examples of α-modification of poly(ethylene oxybenzoate), poly(ethylene oxide), isotactic poly(methyl methacrylate), and cellulose I. Next the relationship between crystal structures and crystallite moduli (one- and three-dimensional) is discussed. Finally vibrational free energies of two crystal modifications of polyethylene are derived and discussed.

Influence of structure on the dynamic mechanical properties of crystalline polymers

Abstract A dynamk mechanical theory is presented whose structural elements correspond to such physically measurable material parameters as the compliance of the phases, the percent crystallinity, and the orientation of the crystalline and noncrystalline regions. The theory is tested by using both structural and dynamk mechanical data from samples of isotactic polyproylene films of varying crystallinity and orientation. For the specific case of isotactic polypropylene the general theory is shown to reduce to a simple two-parameter model. It is further shown that the two-parameter model not only identifies the unique properties of each of the phases separately, but also predicts the dynamic mechanical properties of the polymer over a temperature range of—130°C to 120°C, for samples ranging from unoriented to highly oriented, and varying in crystallinity from 40 to 70%. The model can also predict the dynamic mechanical properties over the same temperature range for strips of these samples cut at varying angl...

Influence of medium on physicomechanical properties of crystalline polymers

Influence of medium on physicomechanical properties of crystalline polymers

Physical and physicochemical modification of polymers

Research on the modification of the properties of crystalline polymers by changing their physical structure is reviewed. Two different modification principles are considered — the creation of a homogeneous physical structure (introduction of small amount of highly dispersed regulators of the structure-forming processes) and the creation of an inhomogeneous physical structure (by contact with large regulating surfaces) in order to differentiate the surface from the bulk properties and improve resistance to the development of defects. The question of regulation of the processes of physical structure formation by the introduction of chemically reacting substances is also investigated. The possibilities of using antioxidants as physical modifiers and the possibility of physical modification during both the processing and synthesis of polymers are stressed.

Morphology and Properties of Crystalline Polymers with Fiber Structure

The morphological properties as derived from wide- and small-angle x-ray scattering, IR dichroism, electron spin resonance, and electron microscopy, and the anisotropy of mechanical properties of the fiber structure can be well explained by the microfibrillar concept developed on the basis of a detailed study of plastic deformation and fracture of polymer single crystals. The microfibrils bridging the cracks of a fractured crystal contain in axial direction a regular alternation of crystal blocks and amorphous layers containing chain folds, chain ends and a large ratio (between 5 and 30%) of tie mole cules providing the high longitudinal elastic modulus and strength. With lateral dimensions between 100 and 300 Å and a length of about 10 μ, they represent the strong structural element of the fiber. Lateral fit of crystal blocks of adjacent microfibrils produces the lamellae oriented more or less perpendicular to the fiber axis. They are a secondary structural element contributing to the lateral elastic modulus and strength. But the relatively easy axial slip of microfibrils, not substantially hampered by lamellae, yields the high shear compliance which is inexplicable by any model based on lamellae as primary element of fiber structure. The fracture of fibers in the tensile test most probably initiates at point defects of the microfibrillar or fibrillar superlattice, i.e., at the ends of microfibrils. The density of such defects as derived from the probable dimensions of microfibrils agrees very well with the observed number of ruptured chains.

結晶性高分子の粘弾性-とくにポリエチレンについて

結晶性高分子の粘弾性-とくにポリエチレンについて

Structure and Properties of Crystalline Polymers

Through control of the crystallization process many polymers can be made to exhibit a broad spectrum of structural possibilities, ranging from a state of high disorder to one of high order. Emphasis has been placed on bulk-crystallized polymers which normally fall near the center of this spectrum. This was done in part because polymers are most commonly fabricated in this manner, and also because the amount of attention given in recent years to crystals grown from dilute solution has tended to obscure important aspects of the structure of bulk-crystallized polymers. Differences in the structure of the interlamellar regions account most reasonably for many of the variations in mechanical properties that crystalline polymers can be made to display. The interlamellar amorphous model, proposed here as a structural model for bulk-crystallized polymers, largely neglects the lamellae themselves, because so little is known about the structure of the lamellae of bulk-crystallized polymers and how variations in lamellar structure can affect properties. This model is intended, therefore, as both a working hypothesis to aid further investigation and as an outline to be filled in as more is learned about the supramolecular structure of crystalline polymers (31).

Molecular Mechanics of Point Defects in Polyethylene

Certain properties of crystalline polymers can be associated with the presence of local defects, e.g., deviations of short segments of the chain from the predominant conformation allied with the crystal structure. General methods are developed by which such chain defects may be simulated by computer techniques. The application of these methods to the polyethylene system gives detailed information concerning: stable defect structures, low-energy conversion paths between stable structures (molecular motions), interactions in defect assemblies, and intermolecular interactions between chains and crystalline environments. Such an investigation of all fold structures containing seven (or less) dihedral angles indicates the existence of a small number of stable but immobile structures. The intramolecular energy of these structures is somewhat high and they do not pack efficiently. Expansion of fold structures to include eight and nine dihedral angles and slight relaxation of orientation constraints provides lower-energy structures which are mobile, more efficient packing, and a low-energy path for conversion between diagonal and b-axis folds. In addition, stable structures and motions of other local defects (i.e., kinks and jogs) are identified, rigid segment rotation is found to be questionable, and certain mechanical properties are interpreted in terms of the over-all results.

Effect of fillers on the supramolecular structures and mechanical properties of crystalline polymers

Effect of fillers on the supramolecular structures and mechanical properties of crystalline polymers