Prominently Promoting the Formation of Poly(butylene adipate) <Emphasis Type="Italic">α</Emphasis>-Form Crystals by Coalescing from Inclusion Complex

We successfully use a co-precipitation method to prepare inclusion complex between poly(butylene adipate) (PBA) chains (guest component) and urea molecules (host component). The PBA/urea inclusion complex is confirmed to adopt a hexagonal crystal modification with lattice parameters of a = 8.14 Å and c = 10.92 Å, and the interaction between PBA chains and urea is van der Waals force. The singly isolated PBA chains are suggested to take some gauche conformation, which is different from the all-trans conformation in β-form PBA. Furthermore, we employ the isolated PBA chains which are uniformly pre-established in a specific conformation in urea channels to regulate the crystal form of PBA for the first time. After removing the host urea molecules, the coalesced PBA chains are found to solely crystallize into α-form crystals at different coalescing temperatures. By comparing the FTIR spectra, it is found that PBA chains in inclusion complex plausibly contain some similar conformers as those in α-form crystal, which is suggested to be the intrinsic reason for the sole formation of α-form crystals. This research proves that inclusion complex can be used as a very effective method to regulate polymorphism of semi-crystalline polymers.     

Inclusion Compounds Formation of Poly(azomethine ether)s and β‐Cyclodextrin

In this study, two poly(azomethine ether)s were synthesized and they can form inclusion compounds (ICs) with β‐cyclodextrin (β‐CD). Fourier transform infrared (FTIR) spectroscopy, ¹H nuclear magnetic resonance spectroscopy (¹H‐NMR), thermogravimetric analysis (TGA), X‐ray diffraction (XRD) have been utilized to observe the formation of polymer‐CD‐ICs. The differentiation in their FTIR spectra may indicate the formation of the inclusion compounds between poly(azomethine ether)s and β‐CD. Compared the ¹H‐NMR of polymer‐CD‐ICs with β‐CD, proton signals belonging to both β‐CD and poly(azomethine ether)s can be found in the spectrum. The chemical shift of the protons H‐3, H‐5 has changed after the formation of inclusion compounds, which is perhaps due to the interaction of these protons with polymers. TGA scans showed the much higher decomposition temperatures observed for two polymer‐CD‐ICs may imply that polymer chains included inside the β‐CD's cavity can greatly improve β‐CD's stabilities. The X‐ray diffraction patterns were confirmed to be the new crystal structures.     

Crystallization of Poly(ethylene adipate) within γ-Phase Poly(vinylidene fluoride) Matrix

The effects of PEA on the γ-phase PVDF crystal structure and the crystallization of PEA within the pre-existing γ-phase PVDF spherulites have been investigated by optical microscopy(OM), infrared spectroscopy(IR) and scanning electron microscopy(SEM). The results demonstrate that the γ-phase PVDF spherulites consist of the lamellae exhibiting a highly curved scroll-like morphology and develop preferentially in PEA-rich blend. With increasing PEA concentration, the scroll diameter increases and the scrolls are better separated from each other. PEA crystallizes first in the interspherulitic region and transcrystalline layer develops. Subsequently, the transcrystalline layer of PEA continues to grow within the γ-phase PVDF spherulites, e.g., in the region between the scrolls, until impinging on other PEA transcrystalline layers or spherulites. The crystallization kinetics results indicate that the growth rate of PEA crystals in the intraspherulitic region of γ-phase PVDF shows a positive correlation with content of PEA, but a negative one with the crystallization temperature of γ-phase PVDF.     

Flexible Gradient Poly(ether-ester) from the Copolymerization of Epoxides and ε-Caprolactone Mediated by a Hetero-bimetallic Complex

Copolymerization is a commonly employed method for optimizing the properties of polymer materials. Incorporating ether segments into polyesters main chain to obtain polyether-polyester copolymers is an effective strategy to realize the integration of multiple properties of polyester and polyether, and to develop more high-performance, multi-purpose polymer materials. Herein, the synthesis of poly(ether-ester)s is accessible by employing the biphenyl-linked heterodinuclear salen Cr-Al complex in the presence of PPNCl for the copolymerization of epoxides and ε-caprolactone(CL). Monitoring the copolymerization process reveals that catalyst 1 exhibited good performance for the copolymerization of epoxides and CL, affording copolymers with a gradient sequence structure. The dynamic thermomechanical analysis(DMA) study indicates the obtained poly(ether-ester)s possess enhanced flexibility compared with the block copolymers or blend of PPO and PCL homopolymers with the same ratio. This study provides a theoretical basis for the preparation of high-performance polymer materials.     

Aryloxy ‘biometal’ complexes as efficient catalysts for the synthesis of poly(butylene adipate terephthalate)

A comparative study of catalytic activity of aryloxy complexes of Mg, Zn and Al in the synthesis of poly(butylene adipate terephthalate) demonstrated the preference of Al-based catalyst containing two bulky substituents in ortho-position of phenol ligand in terms of higher values of PBAT MW and lower yields of cyclic diester side product.     

Violacein/β-Cyclodextrin Inclusion Complex Formation Studied by Measurements of Diffusion Coefficient and Circular Dichroism

The formation of inclusion compounds between violacein and-cyclodextrin was studied by diffusion and circulardichroism measurements. The present work was undertaken to explore the feasibilityof the -cyclodextrin in reducing the toxicity and enhancing the antitumoral efficacy ofviolacein by forming an inclusion complex. The results of the two experimentsare in good agreement, suggesting the formation of 1 : 1 and 1 : 2 complexes.The diffusion coefficient measurements enabled estimates of the sizes of the complexesinvolved. From the circular dichroism and computational calculations it was possibleto view a preference for inclusion of the most polar part of the molecule to form a1 : 2 inclusion complex. We expect that this work proves the potential of thesetechniques to determining complex stoichiometry.     

α-Brominatjon of Ketones with the Bromine Complex of Poly(styrene-co-4-vinylpyridine)

The bromine complex of poly(styrene-co-4-vinylpyridine) reacted with ketones and 1,3-diketones to form a -bromo or α,α-dibromo products in high yields     

Structural Characterization of Poly(α-Fluoroacrylonitrile) and Poly(Ethyl α-Fluoroacrylate)

Abstract

Monomers α-fluoroacrylonitrile (FAN) and ethyl α-fluoroacrylate (EFA) and homopolymers poly(α-fluoroacrylonitrile) (PFAN) and poly-(ethyl α-fluoroacrylate) (PEFA) have been synthesized and spectroscopi-cally characterized in detail for the first time. The ¹³C- and ¹⁹F-NMR spectroscopic results are reported, and the results are correlated to the tacticity and microstructure of both homopolymers. The major portion of the polymers is atactic. TGA analysis of PFAN indicates that the polymer is stable to about 200°C with subsequent loss of HF. PEFA is stable to 300 °C. Molecular weights determined by intrinsic viscosity (M_v ) are found to be about 130,000 for PFAN, and GPC analysis of PEFA indicates a molecular weight (M_n ) of about 36,000. Dielectric permittivities (ε) for PFAN and PEFA were determined to be 8.9 and 4.0, respectively, at 50 Hz.     

Formation of α,α''''-Bis(substituted benzylidene)cycloalkanones from Masked Aldehydes Promoted by Samarium(III) Triiodide

~~Formation of α,α'-Bis(substituted benzylidene)cycloalkanones from Masked Aldehydes Promoted by Samarium(III) Triiodide~~     

Characterization of Poly(ethyleneoxyethylene terephthalate‐co‐adipate) using NMR Spectroscopy

Comonomer sequence distribution and ¹H‐NMR chemical shifts were determined for poly(ethyleneoxyethylene terephthalate‐co‐adipate) (PEOETA) copolyester. The sequence distribution of terephthalate (T) and adipate (A) residues was found to be random, which is typical for copolyesters synthesized via bulk polycondensation. The inner methylene protons of EOE residues appeared as a pair of doublets due to chemical shift differences among the EOE‐centered dyad sequences TT, TA, AT, and AA. The four equivalent phenylene protons of T residues appeared as a triplet due to chemical shift differences among the T‐centered triad sequences TTT, TTA (?ATA), and ATA. Higher‐order tetrad and pentad sensitivity were also observed for the inner methylene and phenylene protons, respectively, especially for TT‐ and TTT‐centered sequences. The sequence sensitivity of the phenylene protons was attributed to unique spatial interactions between themselves and protons within adjacent adipate and EOE units. These spatial interactions were confirmed using Nuclear Overhauser Enhancement Spectroscopy (NOESY).     

Largely Improved Stretch Ductility and β-Form Room-temperature Durability of Poly(vinylidene fluoride) by Incorporating Aliphatic Polyketone

In this study, we attempt to prepare a new blending system of poly(vinylidene fluoride) (PVDF) and aliphatic polyketone (POK) by melt compounding. The latter is a promising engineering plastic with comprehensive mechanical performances. When POK acted as minor phase to homogeneously disperse in and intimately contact with PVDF matrix, the brittle tensile behavior of neat PVDF transferred into a remarkably flexible manner (the elongation at break increased for 20 times), and more interestingly, the roomtemperature durability of β-form PVDF in the uniaxially drawn blend film was obviously better than that in the neat PVDF film. Fourier transform infrared spectroscopy revealed that specific dipole interaction existed between CF_2 group of PVDF and C=O group of POK.The intermolecular dipolar interaction induced good compatibility in the PVDF/POK blends, as evidently proved by fine two-phase morphology and decreased melting points of POK crystals. Therefore, the good compatibility and interfacial enhancement are responsible for the improvement of the stretch ductility and β-form room-temperature durability of the PVDF/POK blends.     

Influence of Isosorbide on Glass‐Transition Temperature and Crystallinity of Poly(butylene terephthalate)

Copolyesters of isosorbide and 1,4‐butane diol were prepared by Ti(OBu)₄‐catalyzed transesterifications with dimethyl terephthalate in bulk at temperatures up to 250°C. The content of isosorbide was considerably lower than expected from the feed ratio and the molar masses were low, so that no DSC measurements were conducted. Copolycondensations of isosorbide and 1,4‐butane diol with terephthaloyl chloride were either performed in dichloromethane at 40°C or in toluene at 100°C. The second method gave the higher molar masses. However, both series of polycondensations had the content of isosorbide roughly paralleled the feed ratios in common. The DSC measurements revealed that even 6 mol% of isosorbide is sufficient to raise the glass‐transition temperature (T_g) by 10–12°C (up to 55°C). With 50 mol% of isosorbide, the T_g reaches 100°C. Yet, incorporation of isosorbide also reduces the melting temperature T_m and the degree of crystallinity, and a mol percentage above 30% prevents crystallization completely. In summary, incorporation of isosorbide allows for fine‐tuning of T_g and T_m of poly(butylene terephthalate) over a wide range.     

Isolation of 2-Chloro-5-methylpyridine from its Isomer 2-Chloro-3-methylpyridine by Formation of its Copper(II) Complex

2-Chloro-5-methylpyridine is an important intermediate for the preparation of biological active compounds, especially insecticides1, e.g. imidacloprid2, and is usually manufac- tured from 3-methylpyridine N-oxide. However, the manufacturing process also forms the by-products: 3-methylpyridine and its isomer 2-chloro-3-methylpyridine3. The pro- perties of the isomers are similar, it is difficult to separate by ordinary methods, such as distillation. Scheme 1 79.4%13.6%5.2%NClCH3NCH3ClNC…     

The Kinetics of Crystallization of Poly(tetrafluoroethylene) by the Action of γ-Radiation

The kinetics of crystallization of PTFE over the temperature range 287–310 K upon its -irradiation to a dose of 220 kGy was studied using calorimetric procedures. Parameters for the models of radiation-induced growth in the degree of crystallinity (expressed as the mass fraction) of bulk and film polymer specimens were calculated. It was shown that the degree of perfection of crystals produced upon irradiation can be determined from the heat of transition at T 293 K characteristic of PTFE.     

Studies of the Interaction of the Salicylideneserinatecopper(II) Complex with β-Cyclodextrin: Characterization and Reactivity of the Inclusion Compound

The compound formed by the copper-Schiff base complex salicylideneserinatecopper(II), [Cu(sal-ser)(H2O)], interacting with -cyclodextrin was prepared, and characterized in the solid state by infrared, UV-visible and EPR spectroscopies, X- ray diffraction, and thermoanalytical techniques. The catalytic activity of this compound, [Cu(sal-ser)CD], in the decomposition of hydrogen peroxide, and in the dismutation of superoxide radicals was also verified, in comparison with the reactivity of the free complex, in aqueous solution. In both cases, a decreasing in the reaction rate was observed for the CD-containing compound. The results of structural characterization, in addition to the substantial differences observed in the catalytic activities of the compounds, are indicative of partial insertion of the copper complex in the cavity of the oligosaccharide.     

Formation of five- and six-membered nitrogen-containing heterocycles on the basis of hydrazones derived from α-dicarbonyl compounds (microreview)

Chemistry of Heterocyclic Compounds - In this microreview we provide a broad coverage of methods used over the previous 20 years for the synthesis of nitrogen-containing heterocyclic structures on...     

Changes in the Solubility of β-Cyclodextrin on Complex Formation: Guest Enforced Solubility of β-Cyclodextrin Inclusion Complexes

The most common native host molecule, -cyclodextrin (cycloheptaamylose) is able toform inclusion complexes with a large variety of guestmolecules (or ions) of different size and shape. Theproperties of the included guest molecule are highlyinfluenced by the host-guest interaction, and thepractical usefulness of -cyclodextrin isdependent on these effects. These changes are mainlyinvestigated from the point of view of the guest andto a lesser extent from that of the host. In spite ofthis, the kind of guests and that of the host-guestinteractions during the formation of the inclusioncomplex seem to influence the properties of thehydrophilic domain of -cyclodextrin (i.e. thatof the supramolecule itself), too, and this effect canbe well demonstrated by the change of solubility ofdifferent -cyclodextrin inclusion complexes.This change can be best correlated with the solubilityof the guest as if the guest enforced its solubilityon the supramolecule.     

Spectrophotometric Studies on the Inclusion Formation of β-Cyclodextrin with 3,4-(Methylenedioxyphenyl) Benzylideneaniline

Complexation of -cyclodextrin with 3,4-(methylenedioxyphenyl) benzylideneaniline has been studied in aqueous solution by means of spectrophotometry. It was observed that the complexation attains equilibrium very slowly. The equilibrium constant of the 1:1 complexation between -CD and MDBA was determined, and its dependence on temperature examined. Findings are discussed in light of host–guest intermolecular interactions. Two possible mechanisms of complexation are proposed.     

Thermal Decomposition of Polyisoprene,Poly(p-isopropyl α-Methylstyrene), and Poly(isoprene/p-isopropyl α-Methylstyrene)

Thermal decompositions of polyisoprene, poly(p-isopropyl α-methylstyrene) (PPIPαMS), and poly(isoprene/p-isopropyl α-methylstyrene) (sample M-32) were carried out at various temperatures in the range 200–340° C in a differential thermo-gravimetric apparatus. The undecomposed polymers as well as their decomposed residues were analyzed by gel-permeation chromatography (GPC), infrared spectroscopy (IR), and nuclear magnetic resonance (NMR). Based on the changes observed in the distribution of molecular weights, depolymerization is the predominant step in the decomposition of PPIPAMS and polymer M-32, whereas random scissions predominate in the case of polyisoprene. The combined data of GPC, IR, and NMR indicate that only interchain reactions leading to the formation of cyclized products are present in the decomposition of polyisoprene while interchain as well as intrachain reactions are operative in the case of polymer M-32.     

Energy-transfer Process Accelerated by the Formation of Electrostatically Stabilized Aggregate (ESAg)

We have proposed that oppositely-charged long-chain molecules with roughly eight to sixteen carbons might form electrostatically stabilized aggregates (ESAgs) by both the hydrophobic-lipophilic interaction (HLI) and the electrostatically attractive force in the concentration range of 10-7 mol/L to 10-5 mol/L1,2. Thus ESAg is yet another structural niche for molecular assemblages in-between the simple aggregate and the micelles. That ESAg species existing at concentrations much lower tha…