THE ORIENTATION AND CRYSTALLIZATION OF POLYETHYLENE TEREPHTHALATE

The drawing behavior of three types of PET spherulites and PET amorphous samples have beenstudied. Two different sample preparation techniques were used in this study: (1) The films withnormal positive, normal negative or abnormal spherulites were prepared by solution casting tech-niques, then the films were deformed by uniaxial drawing. The uniaxial drawing behavior of PETspherulites appears to be dependent on the angles between the c-axis and the radius direction of thespherulites and that the deformation of spherulites becomes more difficult the larger the angles. (2)Amorphous films of PET were prepared first, then the films were deformed under uniaxial drawingto achieve c-axis orientation at a temperature near the glass transition temperature. The orientedfilms were subsequently annealed with fixed length at 215℃The films prepared in this way ex-hibit excellent c-axis orientation along the stretching direction. The degree of perfection of thecrystalline structure is much greater than that of the spherulites.     

THE CRYSTALLIZATION BEHAVIOR OF URETHANE SUBSTITUTED POLYDIACETYLENE

The crystalline behavior of urethane substitute polydiacetylene was studied by using pohrized light and electron microscopy. The lamellar morphological structure was observed in the crystallized films. The thickness of lamellae is about 300A, being independent of the crystalline temperature. But the size and density of lamellae were dependent on the crystallization temperature. If the molten film was sheared during the crystallzation process the oriented lamellae grew with their long axes perpendicular to the direction of shear and the chain direction was normal to the lamellar surface.     

THE PHENOMENON OF CONGLOMERATE CRYSTALLIZATION. PART 50. THE CRYSTALLIZATION BEHAVIOR OF [trans-Co(en)2(NO2)2]ClO4 (I), MESO-[Co-trans-Me-(N-Me-ETHYLENEDIAMINE)2-trans-(NO2)2]ClO4 (II), K[trans-Co(β-ALANINATO)2(NO2)2] (III) AND THE ISOLATION AND PARTIAL STRUCTURAL DESCRIPTION OF (H5O2)[trans-Co(β-ALANINATO)2(NO2)2] (IV)

Abstract

[trans-Co(en)₂(NO₂)₂]ClO₄ (I) crystallizes, at 22°C, from a deionized water solution, as a racemate, in space group P$1 (No. 2), with lattice constants: a = 6.581(2)Å, b = 8.274(1) Å, c = 12.660(3)Å, α = 77.28(2)Å, β = 76.58(2)°, γ = 75.20(2)° V = 638.71;ų and d(calc; MW = 370.59,z = 2) = 1.927gcm^?3. A total of 2233 data were collected over the range of 4° ≤ 2θ ≤ 50° of these, 1961 (independent and with I ≤ 3σ(I)) were used in the structural analysis. Data were corrected for absorption (μ = 15.989 cm^?1) and the relative transmission coefficients ranged from 0.6792 to 0.9874. The final R(F) and R≤(F) residuals were, respectively, 0.0738 and 0.0763. Two half cations are located at inversion centers; the anions are in general positions.

meso-[Co-trans-Me-(N-Me-ethylenediamine)₂-trans(NO₂)₂]ClO₄ (II) [(N-Meen) = N-methyl-ethylenediamine] crystallizes at 22°C, from a deionized water solution in space group Pbca (No. 61) with lattice constants: a = 16.882(5) Å, b = 11.990(3) Å, c = 15.017(5) Å; V = 3039.72 ų and d (calc;MW = 398.64, z = 8) = 1.742g cm^?3. A total of 5281 data were collected over the range of 4° ≤ 2θ ≤ 50° of these, 1779 (independent and with I ≤ 2.5σ(I) were used in the structural analysis. Data were corrected for absorption (μ = 13.501 cm^?1 and the transmission coefficients ranged from 0.7956 to 0.9947. The final refinement of the structure (anisotropic thermal parameters for the heavy atoms; idealized hydrogens for the cation) are R(F) = 0.045 and R_w (F) = 0.052). The -NO₂ ligands are trans to one another in the axial direction while the N-methyl groups are trans to one another across the basal plane. The cations are located in general positions and the torsional angles of the en rings are δ(N1-C1-C2-N2 = 52.0°) and δ(N3-C3-C4-C4 = 51.0°), in contrast with those of (I) which are of opposite helical chirality. This compound is one of two trans-Co(III)X₂ cations of which we are aware that, while sitting at a general position of the space group, has two ethytenediamine rings of the same helical chirality.

K[trans-Co(β-alaninato)₂(NO₂)₂] (III) obtained after several batches of crystals of (TV) had separated from the mother liquor (see Syntheses). (III) crystallizes at 22°C, in space group Cc (No. 9) with lattice constants: a = 12.385(6)Å, b=13.109(5)Å, c = 8.290(5)Å, β=115.19° V = 1217.97 ų and d(calc; MW = 366.22, z = 4) = 1.997 g cm^?3. A total of 1238 data were collected over the range of 4° ≤ 2θ 50° of these, 1016 (independent and with I ≤ 2.5σ(I) were used in the structural analysis. Data were corrected for absorption (μ 17.90cm^?1) and the transmission coefficients ranged from 0.5322 to 0.6627. The final R(F) and R_w (F) residuals were, respectively 0.020 and 0.022. Solution of the structure, using the first batch of crystals, proved that the compound isolated was the (H₅O₂)⁺ derivative (see below and Discussion). A later batch of crystals contained (III). We have previously observed the precipitation of hydronium salts, trapped by amine carboxylato salts of cobalt (see Discussion). The anions consist of two six-membered rings formed by the metal and two (O,N)-bound β-alaninato ligands; and, both have chair conformations.

(H₅O₂) [trans-Co(β-alaninato)₂(NO₂)₂] (IV) is the substance that first crystalized from an aqueous solution of (III) (see Experimental). It crystallizes, at 22°C, in space group Cc (No. 9) or C2/c (No. 15) with lattice constants: a=12.389(39)Å, b=13.120(11)Å, c=8.299(9) Å, β=115.09(19)° V=1221.72 ų and d(calc; MW=364.15, z=4) = 1.980 g cm^?3. An incomplete data set of 1592 reflections was collected over the range 4° ≤ 2θ ≤ 50° because the crystal decomposes in air due to rapid loss of water of crystallization, as shown by differential scanning calorimetry. 956 data were independent with I ≤ 2.5°(I) and were used in the structural analysis. Data were not corrected for absorption because of decomposition of the crystal. The final R(F) and R_w (F) residuals were, respectively, 0.14 and 0.16. To the precision of such a data set, the anions are identical with those found in (III); however the cation, which sits at an inversion center, consists of a proton sandwiched between the oxygens of two waters thus forming (H₅O₂)⁺ cations similar to those we have described in the past (see Refs. [15–18]).     

THE PHENOMENON OF KRYPTORACEMIC CRYSTALLIZATION. PART 1. COUNTERION CONTROL OF CRYSTALLIZATION PATHWAY SELECTION. PART 4. THE CRYSTALLIZATION BEHAVIOR OF (+/−)-[Co(tren)(NO2)2]Br(I), (+/−)-[Co(tren)(NO2)2]2Br(ClO4) · H2O(II), (+/(−)-[Co(tren)(NO2)2]ClO4(III) AND ATTEMPTS TO SOLVE THE STRUCTURE OF (+/−)-[Co(tren)(NO2)2]NO3(IV)

Abstract

Racemic aqueous solutions of (+/?)-[Co(tren)(NO₂)₂]Br (I), (+/?)-[Co(tren)(NO₂)₂]ClO₄ (III) and [Co(tren)(NO₂)₂]NO₃(IV) crystallize as racemates. By contrast, the double salt, (+/?)-[Co(tren)(NO₂)₂]₂Br(ClO₄) · H₂O(II), produces kryptoracemic crystals belonging to the enantiomorphic space group P2₁2₁2₁ (No. 19). The former three species crystallize with one molecule in the asymmetric unit; in the latter, a racemic pair is the asymmetric unit, a fact which is hidden by the enantiomorphic nature of its space group – thus the name of the crystallization phenomenon reported. In (II) pairs of cations are related by an approximate, non-crystallographic, inversion center. The crystal structure and polarity of (I) and the absolute configuration of (II) were determined by refinement. The crystalline contents of (I) to (III) consist of infinite strings of hydrogen bonded cations, the counter ions and (where relevant) waters of crystallization acting as a hydrogen-bonding glue linking the spiral strings

In (II), the N-CH₂-CH₂-NH₂-Co rings of Co(1) are (δδλ) and those of Co(2) are (λλδ) and adjacent strings are linked by the counter-anions and the water of crystallization. Pairs of Co(1) and of Co(2) cations are hydrogen bonded to one another by two N-O···H-N linkages. Finally, pairs of composition Co(1)-Co(1) as well as of Co(2)-Co(2) share another pseudo-inversion center which is approximately valid for the CoN₆ portion of each cation. Since the atoms of the cation are ordered, it is impossible for the pseudo-inversion center to be valid for the -CH₂-CH₂- fragment of the Co(1)-Co(1) or of Co(2)-Co(2) pairs. (I) and (III) crystallizes as racemates whose five-membered rings have chiroptical symbols (δδλ), or its enantiomer.     

A STUDY ON THE CRYSTALLIZATION KINETICS OF NYLON 1010

The kinetic behavior of isohermal and nonisothermal crystallization of nylon-1010has been studied by means of dilatometry and differential scanning calorimetry, respec-tively. The isothermal and nonisothermal process can be descibed by Avrami equationand Ozawa equation, respectively. From the experimental results the kinetic paramters ofcrystallization and crystalline mechanism for isothermal and nonisothermal measurementsare discussed.     

THE STRUCTURE OF N-METHYL-CINNOLINE TCNQ_2 II.THE STRUCTURE OF IN-METHYL-CINNOLINE TCNQ_2

<正> M =553.6, triclinic,Pl, a=6.5157(22), b=7.7153(14), c=13.9146(28)A; α=88.394(16)°, β=84.288(22)°, γ=78.749(22)°, V=682.62(30)A3, Z=1; μ(MoKα)= 0.80cm-1, F(000)=284.92, room temperature. The final R=0.0537 for 1230 independent reflections. Planar tetracyanoquinodimethane(TCNQ). stacks along a axis with the molecular planes parallel to each other. The separations between TCNQs are 3.2698 and 3.2448. The overlaps of TCNQs are of the ring-external bond type. This mode of TCNQ stacking is used to explain the conductivity of the title compound. The D.C. conductivity along needle axis is σ(RT)=10(Ωcm)-1 1.     

THE STRUCTURE OF N-METHYL-CINNOLINE TCNQ_2 I.THE STRUCTURE OF 2N-METHYL-CINNOLINE TCNQ_2

<正> M =553.6 triclinic Pl a=7.5701(9), b=7.5987(1), c=13.0327(13)A; α=86.923(10)°, β=80.921(9)°, γ=69.393(10)°, V=692.92(15)A3, Z=1; μ(MoKα= 0.79cm-1 F(000)=284.92,room temperature. The final R=0.047 for 1736 independent reflections. Planar tetracyanoquinodimethane(TCNQ) stacks along b axis with the molecular planes nearly parallel to each other, and mixed with 2N-methylcinnoline(2N-MCi). The separations between TCNQs are 3.212A and 3.321 A. Two overlap types are quite different. One is of ring external bond overlap, while the other has hardly direct overlap. This feature of 2N-MCiTCNQ2 stacking is used to explain the semiconducting character of the title compound.     

THE EFFECT OF CLAY DISPERSION ON THE CRYSTALLIZATION AND MORPHOLOGY OF POLYPROPYLENE／CLAY COMPOSITES

PP/clay composites with different dispersions, namely, exfoliated dispersion, intercalated dispersion and agglomerates and particle-like dispersion, were prepared by direct melt intercalation or compounding. The effect of clay dispersion on the crystallization and morphology of PP was investigated via PLM, SAXS and DSC. Experimental results show that exfoliated clay layers are much more efficient than intercalated clay and agglomerates of clay in serving as nucleation agent due to the nano-scale dispersion of clay, resulting in a dramatic decrease in crystal size (lamellar thickness and spherulites) and an increase of crystallization temperature and crystallization rate. On the other hand, a decrease of melting temperature and crystallinity was also observed in PP/clay composites with exfoliated dispersion, due to the strong interaction between PP and clay. Compared with exfoliated clay layers, the intercalated clay layers have a less important effect on the crystallization and crystal morphology. No effect is seen for samples with agglomerates and particle-like dispersion, in regard to melting temperature, crystallization temperature, crystal thickness and crystallinity.     

A MECHANISTIC STUDY OF THE FORMATION OF [Ru6C(CO)16]2− FROM [Ru6(CO)18]2−

Abstract

The kinetics of the transformation of [Ru₆(CO)₁₈]^2? into [Ru₆C(CO)₁₆]^2? in diglyme over the temperature range 130–160°C have been determined. The results are consistent with reversible loss of a carbonyl ligand from [Ru₆(CO)₁₈]^2?, followed by formation of carbon dioxide and reassociation of carbon monoxide to give the observed product. Mass spectral analysis of the evolved carbon dioxide trapped as barium carbonate supports an intramolecular pathway for the disproportionation of carbon monoxide.     

THE STRUCTURE OF AGGREGATION STATE AND ISOTHERMAL CRYSTALLIZATION KINETICS OF NYLON-1010

The structure of aggregation state and isothermal crystallization behavior of Nylon-1010 have been studied by WAXD, DSE, Variance-Range Function and density measurement. The results show that crystallization of Nylon-1010 has the most suitable annealing temperature, the crystals of the Nxlon-1010 are two-dimension heterogeneous nucleation. Both low treatment temperature and high crystallization te, temperature are disadvantageous for Nylon-1010 crystal growth.     

CRYSTALLIZATION AND PRELIMINARY CRYSTALLOGRAPHIC DATA OF THE MUNG BEAN INHIBITOR

The trypsin inhibitor from mung bean has a molecular weight of 7984, consisting of two active domains and seven disulfide bonds. It belongs to the Bowman-Birk inhibitor. This inhibitor has been crystallized in two crystalline forms either by dialysis or by batch method. One is tetragonal with unit cell of symmetry P4_122(or P4_322) and dimensions a=b=49.21, c=158.07, each asymmetric unit containing three molecules. Another is orthorhombic with unit cell of symmetry P2_12_12 and dimensions a=39.65, b=57.18, c=52.02, each asymmetric unit containing two molecules.     

EFFECTS OF COUPLING AGENTS ON THE CRYSTALLIZATION BEHAVIOR OF PP/T-ZnOw COMPOSITES

The objectives of this paper are to understand the crystallization behavior of polypropylene(PP)composites with surface modified tetra-needle-shaped zinc oxide whisker(T-ZnOw).T-ZnOw was surface modified with different coupling agents,such as silane coupling agents(KH-550,KH-560)and titanate coupling agent(NDZ-105),in order to improve the compatibility between PP and T-ZnOw.DSC and POM were used to characterize the melt and crystallization behavior and the crystalline structures of the composites,respectively.The results show that the surface modified T-ZnOw acts as a nucleating agent of PP crystallization,depending on the coupling agent used for modification.KH-550 and KH-560 have more apparent role in improving the interfacial interaction than NDZ-105 and induce PP crystallization at higher temperature and with smaller spherulites size.The results also suggest that the crystallization behavior depends on not only the content of coupling agent,but also the content of the surface modified T-ZnOw used in the composites.     

PHOTOPHYSICS STUDIES OF ORCANIC COMPOUNDS (Ⅻ)——THE INVESTIGATION OF THE FLUORESCENCE SPECTRA OF N-SALICYLIDENE-p-(N,N-DIMETHYLAMINO)ANILINE

The fluorescence spectra of N--salicylidene-p-(N,N--dimethylamino)aniline have beeninvestigated in various solvents. Three kinds of fluorescence have been found in the solutionsof various concentrations. They are the excited intermediate (EI) which is formed when theproton transfer has occurred but essentially retains the geometry of the enol tautomer, theexciplex (EX) which consists of a ground monomer and an excited state intermediate and theexcited dimer (ED) which is caused by ground state aggregate. The fluorescence lifetimesof the fluorophores have been measured in tetrahydrofuran (THF). Luminescent mechanismhas been discussed based on the fluorescence spectra and the kinetic data of the compound.     

THE SOLID STATE REACTIONS AND TRANSITIONS IN HIGH POLYMERIC SYSTEMS Ⅲ. THE BULK CRYSTALLIZATION OF LANTHANIDECATALYTICALLY POLYMERIZED POLYDIENES

For the mechanism of isothermal bulk crystallization of high polymers, beside the nucleation and growth steps, the unimpingement of growing crystal aggregates should be taken into account for the modification of the Avrami equation. Starting from Poisson distribution function of growing crystal aggregates, the probability of the unimpinging ones should be P(0)+P(1), then the Q-modified Avrami equation thus derived can be expressed aswhere V0 represents the volume fraction of crystal aggregates at crystallization time t at a given temperature, while the exponent n on t relates to the mode of nucleation and growth, and K_q is the corresponding shape factor. This Q-modified one is verified satisfactory by the isothermal bulk crystallization of lanthanidecatalytically polymerized polybutadiene (Ln-PB), polyisoprene (Ln-PIR) and their copolymers (LnPB/IR). Furthermore, the proposed mechanism is well identified by the change of morphological state during the course of crystallization of the corresponding east film of Ln-PB TR (92/8) at-60°(Fig. 1).Upon examination of the influence of the number of entanglement on crystallization rate, it reveals the existence of two stages of entanglementation, the primary and the secondary ones (Fig. 19)The equation for dependence of molecular weight and entanglement on bulk crystallization rate has been derived as Eq. 13 or 18 for Ln-PB, and verified by the experimental rate data of well fractionated Ln-PB samples crystallized at -9.1 to -15℃(Fig.20).     

STUDIES ON THE MECHANICAL PROPERTIES AND CRYSTALLIZATION BEHAVIOR OF POLYETHYLENE COMPOSITES

The effects of inter facial modifier on the mechanical, dynamic mechanical properties andcrystallization behavior of the polyethylene composites were investigated in the present paper.It was found that the interfacial modifer significantly improved the mechanical properties,influenced the dynamic mechanical spectra and slightly changed the crystallization behavior.The results showed that the interfacial modifier changed the dispersion state of dispersedphase of the composites, resulting in different phase structure, which was the major reasonIeading to different mechanical and crystallization properties.     

KINETICS OF NON-ISOTHERMAL CRYSTALLIZATION OF POLY (ETHYLENE TEREPHTHALATE) MODIFIED BY POLY (ETHYLENE GLYCOL)

The non-isothermal crystallization kinetics of poly(ethylene terephthalate) (PET) modified by poly (ethlene glycol) (PEG) were determined by DSC. The dual linear regression method was used to evaluate the relationship between the reciprocal of t 1/2 ( the half life of crystallization) and the appropriate temperature variable. The parameters such as the activation energy (Ed) for transport, the equilibrium melting temperature (T_m~0),the nucleation parameter (ψ),themaximum crystallization temperature (T_(e, max)), and the kinetic crystallizability (G) for the copolyesters were obtained. The influence of the PEG content in PET chains on the parameters characterizing crystallization kinetics and crystallization thermodynamics was discussed.     

THE PREPARATION,STRUCTURE AND PROPERTES OF Sr_(0.5)Ca(0.5)CuO_2

Sr_(0.5)Ca_(0.5)CuO_2 has been synthesized by the solid state reaction.Thecompound crystallizes in an orthorhombic unit cell,space group D_(2h)~(17)-Cmcmwith a=3.444 ,b=16.11 ,c=3.868 .It decomposes shove 1038℃.Sr_(0.5)Ca_(0.5)CuO_2 is s black p-type semiconductor with resistivity 53Ω.cmat room tempersture.     

CRYSTAL AND MOLECULAR STRUCTURES OF THE DERIVA-TIVES OF ( + )- 1K, 3K(S) , 5S-2,4,3-DIAZAPHOSPHABICYCLO-[3. 2. 1]OCTANE

<正> Compound C9H19N2OPS (1) , Mr = 234. 3, monoclinic, space group P21, a = 7. 5637(2), b = 7. 704(2), c=10. 258(1) (?) ,β = 98. 66(2)°, V = 590. 9(?)3, Z =2, Dc=1. 317g/cm3, F(000) = 252. The final R = 0. 063 and Rw = 0. 080 with unit weight for 870 observed reflections (I≥3σ(I)). Compound C10H22 N3PS(2), Mr = 247. 34, monoclinic, space group P21, a = 7. 656(1), b = 8. 248 (1), c=10.750(l)(?), β=91.31(1)°, 7 = 678.73(?)3, Z = 2, Dc=1. 21g/cm3, final R = 0. 066 and Rw = 0. 081 with unit weight for 813 observed reflections (I≥3σ (I)), F(000) = 268. Both skeletons of (1) and (2) have similar geometry, which is composed of three rings : a seven-membered ring in a boat form, a six-membered ring in a chair conformation, and a five-membered ring in envelope form. The configura-tions of the chiral phosphorus atoms are assigned as 3R for (1) and as 3S for (2).     

CRYSTALLIZATION BEHAVIOR OF PURE AND ADDITIVE-CONTAINING POLY (ETHYLENE TEREPHTHALATE)

The isothermal crystallization of poly (ethylene terephthalate ) (PET),which is free of catalyst, stabilizer, oligomer and diethylene glycol (DEG), was studied by DSC. The crystallization behaviour of pure PET is different from commercial PET and a reasonable explanation is presented. The influences of catalyst, stabilizer, oligomer and DEG on the crystallization of pure PET were examined. It is shown that catalyst (Manganese acetate)and stabilizer (Triphenyl phosphite) result in an increase of the crystallization rate of PET; on the contrary, DEG and oligomer (cyclotetramer) result in a reduction of the crystallization rate. When catalyst and stabilizer coexist together, both of them promote the crystallization at lower temperature ,only a smaller effect was found at higher temperature, it is evident that metal phosphite is formed between the catalyst and stabilizer at higher temperature.