Isothermal Crystallization Kinetics and Crystalline Morphologies of Poly(butylene adipate-co-butylene 1,4-cyclohexanedicarboxylate) Copolymers

In this study, the isothermal crystallization kinetics and crystalline morphology of poly(butylene adipate-co-butylene 1,4-cyclohexanedicarboxylate)(PBAC), which refers to a copolyester containing a non-planar ring structure, were investigated by differential scanning calorimetry and polarized optical microscopy, and compared with those of neat poly(butylene 1,4-cyclohexanedicarboxylate)(PBC). The results indicate that the introduction of butylene adipate(BA) unit into PBAC did not change the intrinsical crystallization mechanism. But, the crystallization rate and ability, and equilibrium melting temperature of PBAC copolymers were reduced. All PBC and PBAC copolymers could only form high density of nucleation from melt at given supercooling, while no Maltese cross or ring-banded spherulites could be observed. PBAC copolymers with a high amount of BA unit became amorphous after quenching with liquid nitrogen from melt, while PBC and PBAC copolymers with a low amount of BA unit could still form a large amount of nuclei under the same treatment.     

Synergistic effect of nucleation and compatibilization on the polylactide and poly(butylene adipate-<Emphasis Type="Italic">co</Emphasis>-terephthalate) blend films

Polylactide (PLA) films blended with 10 wt% poly(butylene adipate-co-terephthalate) (PBAT) were prepared by using a twin screw extruder in the presence of the nucleating agent of titanium dioxide (TiO₂) and the compatibilizers of toluene diisocyanate (TDI) and PLA-grafted-maleic anhydride (PLA-g-MA). The synergistic effect of the nucleation and compatibilization on the properties and crystallization behavior of the PLA/PBAT (PLB) films was explored. The results showed that the addition of TiO₂ significantly enhanced the tensile strength and the impact tensile resistance of the PLB films while slightly decreased its thermal stability. In addition, the compatibilizers of TDI and PLA-g-MA in the system not only affected the crystallinity and cold crystallization process of the PLB films, but also increased the mechanical properties of them due to the improvement of the interfacial interaction between PLA and PBAT revealed by the morphological measurement. The synergistic effects of the nucleating agent and the compatibilizer afforded the blend films with increased tensile strength and impact tensile toughness, improved cold crystallization property and χ _c.     

Synthesis and properties of organic-inorganic hybrid P(NIPAM-<Emphasis Type="Italic">co</Emphasis>-AM-<Emphasis Type="Italic">co</Emphasis>-TMSPMA) microgels

Utilizing the hydrolysis and condensation of the methoxysilyl moieties, organic-inorganic hybrid poly(N-isopropylacrylamide-co-acrylamide-co-3-(trimethoxysilyl)propylmethacrylate) P(NIPAM-co-AM-co-TMSPMA) microgels were prepared via two different methods. The first method was that the microgels were post-fabricated from the crosslinkable linear P(NIPAM-co-AM-co-TMSPMA) terpolymer aqueous solutions above the lower critical solution temperature (LCST) of the terpolymer. For the second method, the microgels were directly synthesized by conventional surfactant free emulsion copolymerization of NIPAM, AM, and TMSPMA. The hydrodynamic diameter and stability of the resultant P(NIPAM-co-AM-co-TMSPMA) microgels strongly depend on the pH and temperature of the microgel aqueous solution. The hydrodynamic diameters of the microgels decreased with increasing the measuring temperature. The phase transition temperature of the microgels was found to be around 34°C, which was independent of the initial terpolymer concentration and shifted to lower temperature with increasing the preparation temperature. Increasing the initial amount of AM will enhance the instability of the microgels at high pH values. Moreover, the P(NIPAM-co-AM-co-TMSPMA) microgels obtained from the linear terpolymer had more homogeneous microstructures as compared with the corresponding NIPAM/AM/TMSPMA microgels prepared by one step emulsion copolymerization as revealed by light scattering measurements.     

Crystallization Behaviors and Regime Kinetics Analysis of Poly(<Emphasis Type="Italic">L</Emphasis>-lactide)-poly(butylene adipate)-poly(<Emphasis Type="Italic">L</Emphasis>-lactide) Based Multiblock Thermoplastic Polyurethanes

Poly(L-lactide)-based (PLLA) poly(ester-urethane)s are particularly relevant and gain significant attention due to their environment-friendly degradability and elastomeric shape memory capability. The tensile properties, resilience and degradation are strongly affected by their crystallization. This work was to investigate crystallization behaviors of the poly(L-lactide)-poly(butylene adipate)-poly(L-lactide) (PLLA-PBAPLLA) based thermoplastic polyurethane elastomers (PLAEUs) we synthesized previously. Dynamic scanning calorimetry (DSC) and polarized optical microscopy (POM) in combination with Avrami, Jezioney and Hoffman-Weeks models were used to analyze the impact of the PLLA block length on the crystallization temperature T_c, degree of crystallinity X_c, nucleation and spherulite growth mode and crystallization regime kinetics of the PLAEUs. The results indicate the low melting point poly(butylene adipate) (PBA) block resides in the amorphous domains while the PLLA block resides in both crystalline and amorphous phases. The X_c of the PLAEUs increase with the increased length of the PLLA block (i.e. higher content of PLLA block). The analyses with Avrami and Jezioney models show the PLAEU copolymers follow a disc-like spherulite growth. The covalently bonded PBA block decreases both nucleation velocity and spherulite growth rate in the isothermal crystallization. Such an impact is lessened as PLLA block length increases. The PLLA homopolymers demonstrate crystallization regime transition from II to III at a certain T_c of isothermal crystallization, while the crystallization regime kinetics of PLLA block in the PLAEUs are explained by a single regime III at low molecular weights of PLLA and the transition is restored as the PLLA block length increases (i.e. regime II to III).     

Novel terpolymers of poly(<Emphasis Type="Italic">p</Emphasis>-dioxanone-<Emphasis Type="Italic">co</Emphasis>-trimethylene carbonate-<Emphasis Type="Italic">co</Emphasis>-L-phenylalanine): Synthesis,characterization, thermal properties and copolymerization mechanism

In order to exploit the biological functions of materials, a series of new random terpolymers were synthesized by the ring-opening polymerization of p-dioxanone, trimethylene carbonate, and L-phenylalanine N-carboxyanhydride (L-Phe- NCA) in the presence of stannous octoate. The terpolymers were characterized by ¹H-NMR, ¹³C-NMR, FTIR, and gel permeation chromatography. The effects of the reactant ratio, catalyst dosage, reaction temperature and time on the copolymerization were investigated, and were found to regulate the composition of the terpolymer. Increases in the reaction temperature, polymerization time, L-Phe-NCA monomer amount, and catalyst content generated a product with a slightly decreased molecular weight. The crystallinity of the terpolymer was investigated by differential scanning calorimetry and polarized optical microscopy. A reasonable mechanism for the polymerization was proposed based on the obtained results.     

Biodegradable poly(butylene succinate-<Emphasis Type="Italic">co</Emphasis>-butylene dimerized fatty acid)s: Synthesis,crystallization, mechanical properties,and rheology

Poly(butylene succinate-co-butylene dimerized fatty acid) (P(BS-co-BDFA)) copolyesters were synthesized from succinic acid (SA) and dimerized fatty acid (DFA) with 1,4-butanediol (BDO) through a two-step process of esterification and polycondensation. The polyester compositions and physical properties of copolyesters were investigated by GPC, ¹H NMR and ¹³C NMR, DSC, WAXD, DMA, TGA, tensile and rheology test. The melting temperature (T_m), and crystallization temperature (T_c) decreased gradually as the content of DFA monomer increased. P(BS-co-BDFA) copolyesters showed the same crystal structure as the PBS homopolyester. Besides, TGA results indicated that P(BS-co-BDFA)s were of higher thermal stabilities. Moreover, it was found that the synthesized P(BS-co-BDFA)s showed the maximum elongation at break (591%) as the DFA contents were 10 mol%. Rheology analysis indicated that the viscoelastic behavior of the polyesters greatly depended on the molecular weight of polyesters.     

Preparation,characterization and morphological study of poly(<Emphasis Type="Italic">m</Emphasis>-toluidine-<Emphasis Type="Italic">co</Emphasis>-<Emphasis Type="Italic">m</Emphasis>-aminoacetophenone) conductive copolymer

A new series of copolymers of poly(m-toluidine-co-m-aminoacetophenone) were synthesized by the chemical oxidative method in acid medium. The copolymers were characterized by UV–Vis and FTIR spectroscopy. X-ray diffraction analysis revealed the partial crystalline nature of copolymer. The morphological study by SEM analysis indicated that the surface of the copolymer had the granular structure of agglomerated morphology with average particle size of 200 nm. The conductivity of the copolymers ranged from 2 × 10^–4 to 3.3 × 10^–8 S/cm and the conductivity decreased with the increase of comonomer concentration. The resultant copolymers showed an enhanced solubility and an improved processability when compared with pure polyaniline.     

Biosynthesis and Characterization of Poly (3-hydroxybutyrate-<Emphasis Type="Italic">co</Emphasis>-3-hydroxyvalerate-<Emphasis Type="Italic">co</Emphasis>-4-hydroxybutyrate) Terpolymer with Various Monomer Compositions by <Emphasis Type="Italic">Cupriavidus</Emphasis> sp. USMAA2-4

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-4-hydroxybutyrate) [P(3HB-co-3HV-co-4HB)] terpolymer was produced using Cupriavidus sp. USMAA2-4 via one-step cultivation process through combination of various carbon sources such as 1,4-butanediol or γ-butyrolactone with either 1-pentanol, valeric acid, or 1-propanol. Oleic acid was added to increase the biomass production. The composition of 3HV and 4HB monomers were greatly affected by the concentration of 1,4-butanediol and 1-pentanol. Terpolymers with 3HV and 4HB molar fractions ranging from 2 to 41 mol.% and 5 to 31 mol.%, respectively, were produced by varying the concentration of carbon precursors. The thermal and mechanical properties of the terpolymers containing different proportions of the constituent monomers were characterized using gel permeation chromatography (GPC), DSC, and tensile machine. GPC analysis showed that the molecular weights (M _w) of the terpolymer produced were within the range of 346 to 1,710 kDa. The monomer compositions of 3HV and 4HB were also found to have great influences on the thermal and mechanical properties of the terpolymer P(3HB-co-3HV-co-4HB) produced.     

Synthesis of (<Emphasis Type="Italic">E</Emphasis>)-<Emphasis Type="Italic">N</Emphasis>-(3-alkoxy-4-acyloxyphenylmethylene)-<Emphasis Type="Italic">N</Emphasis>-(<Emphasis Type="Italic">e</Emphasis>-cyclohexyl)amines

Previously unknown E isomers of azomethines (Schiff bases) were synthesized from vanillal and vanillin esters by their reaction with cyclohexylamine.     

Conformations and properties of <Emphasis Type="Italic">O</Emphasis>-Alkyl-<Emphasis Type="Italic">S</Emphasis>-(2-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dialkylamino)-ethylmethylthiophosphonates

Conformers of the biologically active compounds CH₃P(O)(OR)(SCH₂CH₂NR ₂ ^′ ), where (I) R = i-C₄H₉, R′ = C₂H₅ and (II) R = C₂H₅, R′ = i-C₃H₇, are calculated within the AM1 level of theory. The elongated and twisted forms with maximum and minimum distances between a nitrogen atom and those of a phosphorus tetrahedron, respectively, and bearing a syn and anti oriented alkoxy group relative to a phosphoryl oxygen, are studied. It is found that the differences between the energy, electronic, and geometric parameters of these forms are apparent in differences between their properties, e.g., the ability to participate in complexation and protonation, reactions that to some extent simulate the interaction between a substance and a biological object.     

Novel Preparation of Monodisperse Poly(styrene-<Emphasis Type="Italic">co</Emphasis>-divinylbenzene) Microspheres by Controlled Dispersion Polymerization

Poly(styrene-co-divinylbenzene) particles possessing uniform properties are attractive for various chromatographic applications. However, their preparation by dispersion polymerization is rather complicated. Our aim was to prepare monodisperse PS microspheres by dispersion polymerization of styrene with controlled addition of 1 wt % of divinyl benzene. The reaction occurs in a mixture of ethanol with 2-methoxyethanol or 2-ethoxyethanol and is stabilized and initiated by hydroxypropyl cellulose and dibenzoyl peroxide, respectively. The effects of the medium polarity based on changing of the solvent mixture ratio and several modes of divinyl benzene addition, including simple one-shot and continuous divinyl benzene post-addition, on the particle size and morphology are investigated. Slow continuous dosing of 1 wt % of divinyl benzene one hour after the start of the styrene polymerization produce monodisperse spherical PS particles 5.4 μm in size. Such microspheres might be suitable as precursor for a solid adsorbent for harmful and carcinogenic organic vapors.     

Solvent dependent swelling behaviour of poly(<Emphasis Type="Italic">N</Emphasis>-vinylcaprolactam) and poly(<Emphasis Type="Italic">N</Emphasis>-vinylcaprolactam-<Emphasis Type="Italic">co</Emphasis>-itaconic acid) gels and determination of solubility parameters

Swelling behaviour of poly(N-vinylcaprolactam) (PVC) and poly(N-vinylcaprolactam-co-itaconic acid) (P(VC-co-IA)) gels was investigated in different solvents (water, ethanol, methanol, isopropyl alcohol (IPA), chloroform, toluene, acetone) and in binary solvent mixtures (ethanol/chloroform, ethanol/methanol, IPA/chloroform, ethanol/water, IPA/water). Gels were synthesised in ethanol by the free radical cross-linking polymerisation method at 60°C for 24 h in the presence of azo-bis(isobutyronitrile) and allyl methacrylate as the initiator and cross-linker, respectively. And also, ethanol/distilled water mixture (?_r = 4:1) was used as the synthesis medium to determine its effect on the swelling of gels. It was found that the presence of water in the synthesis medium significantly affected the equilibrium swelling value (ESV) and the swelling tendency of gels both in solvents and in solvent mixtures. All gels synthesised in ethanol showed the highest swelling in chloroform. The gels synthesised in the ethanol/water mixture displayed different swelling behaviour. In this case, while chloroform was still valid for maximum swelling of PVC, P(VC-co-IA) had the highest swelling in methanol. Solubility parameters of gels were predicted by the van Krevelen-Hoftyzer (VKH) and Hoy methods (group contribution methods) and theoretical calculations verified the experimental swelling order.     

The Crystallization,Melting Behaviors and Thermal Stability of Cross-linked Poly(3-hydroxybutyrate-<Emphasis Type="Italic">co</Emphasis>-3-hydroxyvalerate) by Octavinyloctasilasesquioxane

A series of cross-linked poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/octavinyloctasilasesquioxane (PHBV/OVS) composites were obtained by a simple melt reactive processing technique. Dicumyl peroxide (DCP) and OVS were employed as a free radical initiator and a cross-linking agent, respectively. The chemical structure of these produced composites were identified by ¹H/¹³C/²⁹Si-nuclear magnetic resonance spectroscopy (¹H/¹³C/²⁹Si-NMR) and Fourier transform infrared spectroscopy (FTIR). The melting behavior, non-isothermal crystallization, spherulite morphology and thermal stability property of PHBV/OVS composites were also investigated. The nucleation behaviors and crystallization rate of PHBV/OVS were significantly enhanced with the formation of cross-linked networks with different side-chains and cross-linking points. The red shift of crystalline peak temperature with addition of a small amount of OVS content evidenced the higher crystalline ability compared with the neat PHBV. However there was a threshold content, beyond which the crystallization rate weakened again. Additionally, the cross-linked structure of PHBV/OVS composites could be adjusted by changing the amount of OVS.     

The influence of the synthesis pressure on the chromatographic properties of poly(divinylbenzene-<Emphasis Type="Italic">co</Emphasis>-ethylvinylbenzene-<Emphasis Type="Italic">co</Emphasis>-2-hydroxyethyl methacrylate) monolithic columns

Monolithic columns based on copolymer of divinylbenzene (DVB), ethylvinylbenzene (EVB), and 2-hydroxyethyl methacrylate (HEMA) were prepared and applied to the separation of low-molecular-weight aromatic compounds. The monoliths were synthesized via thermally initiated free-radical polymerization in confines of stainless steel tubes with dimensions of 100 × 4.3 mm. In order to compensate for the polymer shrinkage during the synthesis and prevent the monolith from detachment from the column wall, the polymerization was conducted under nitrogen pressure. The excess pressure was varied from 0 bar to 9 bar. The synthesis under pressure was shown to improve the peak shapes and column efficiency in comparison with the synthesis in the closed tube. The optimum pressure for poly(DVB-co-EVB-co-HEMA) monoliths was found to be 3 bar. The efficiency of the column obtained at 3 bar is 13 500 TP/m for propylbenzene (k′ = 6) and 38 300 TP/m for uracil (k′ = 0).     

Preparation and polymerization mechanism of dihydroxy-capped PCL,poly(CL-<Emphasis Type="Italic">b</Emphasis>-PEG-<Emphasis Type="Italic">b</Emphasis>-CL) and poly(DTC-<Emphasis Type="Italic">b</Emphasis>-CL-<Emphasis Type="Italic">b</Emphasis>-DTC)

The ring opening polymerization of ε-caprolactone (CL) was initiated by glycol and yttrium tri(2,6-di-tert-butyl-4-methylphenolate)s (Y(OAr)₃), preparing dihydroxy-capped poly (ε-caprolactone) (PCL) with controllable molecular weight. ¹H NMR and SEC analyses indicate that two kinds of active species and corresponding PCL with different structures exist in the system. Increasing the ratio of glycol to Y(OAr)₃ benefits the formation of monofunctional active species. However, poly(ethylene glycol) (PEG)/Y(OAr)₃ system only contains sole bifunctional active species to synthesize copolymer of CL with PEG (poly(CL-b-PEG-b-CL)). Dihydroxycapped PCL as macroinitiator can further initiate the polymerization of 2,2-dimethyltrimethylene carbonate (DTC). Thus, triblock copolymer of CL with DTC (poly(DTC-b-CL-b-DTC)) has been prepared.     

<Emphasis Type="Italic">Z</Emphasis>-and <Emphasis Type="Italic">E</Emphasis>-conformers of <Emphasis Type="Italic">N</Emphasis>-chloroacetylcytisine

N-Chloroacetylcytisine was synthesized by acylation of (–)-cytisine. Stable Z- and E-conformers with respect to rotational isomerism around the N-12–CO bond were found in PMR spectra at room temperature. The point at which PMR resonances of the Z- and E-conformers coalesced upon heating was measured. The transition barrier between the conformers was estimated.     

Synthesis of <Emphasis Type="Italic">ortho</Emphasis>-carboranyl derivatives of (<Emphasis Type="Italic">S</Emphasis>)-asparagine and (<Emphasis Type="Italic">S</Emphasis>)-glutamine

(S)-Asparagine and (S)-glutamine ortho-carboranyl derivatives with free amino and carboxy groups in the α-position were synthesized. By an example of N ^γ-(1,2-dicarba-closo-dodecarboran-3-yl)-(S)-glutamine it was demonstrated that the developed synthetic approach carboranyl derivatives of amino acids allowed the preparation of optically pure isomers.     

Thiocyanation of <Emphasis Type="Italic">N</Emphasis>-arylsulfonyl-, <Emphasis Type="Italic">N</Emphasis>-aroyl-, and <Emphasis Type="Italic">N</Emphasis>-[(<Emphasis Type="Italic">N</Emphasis>-arylsulfonyl)benzimidoyl]-1,4-benzoquinone imines

Reactions of thiocyanate ion with N-aroyl-, N-arylsulfonyl-, and N-(N-arylsulfonylbenzimidoyl)-1,4-benzoquinone imines follow the 1,4-addition pattern, and the adducts undergo intramolecular cyclization to give the corresponding N-substituted 5-amino-1,3-benzoxathiol-2-ones as final products.     

Molecular structure of <Emphasis Type="Italic">N</Emphasis>-(<Emphasis Type="Italic">o</Emphasis>-and <Emphasis Type="Italic">p</Emphasis>-hydroxybenzyl)cytisine

The molecular structures of N-(o-and p-hydroxybenzyl)cytisine were investigated by NMR spectroscopy, x-ray structure analysis, and molecular modeling. It was found that NMR resonances of the OH and aromatic protons in N-(o-hydroxybenzyl)cytisine were doubled because of the presence of two conformers in solution. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 165–168, March–April, 2008.