Thermal Properties and Morphology of Poly(Ester-Urethanes) Prepared from Polycaprolactone-Diol

The soft segment crystallinity and morphology of poly(ester-urethanes) (PEUs) based on poly(ε-caprolactone) (PCL) as a soft segment and an aliphatic diisocyanate in the hard segment were studied. It was found that the restriction of the crystallization of the PCL soft segment depends on the hard segment concentration, the length of the soft segment, and the total molecular mass of the PEUs. The PEU based on a low molecular mass PCL (M=2000) is an amorphous elastic material during a long time after casting from solution or after melt crystallization. A soft-hard segment endothermal mixing transition (T_mix) of about 70-80°C is observed in the DSC curves of this PEU sample. This revised version was published online in August 2006 with corrections to the Cover Date.     

Extraction-spectrophotometric investigations on two ternary ion-association complexes of gallium(III)

Complex formation and liquid-liquid extraction were studied in systems containing Ga(III), azoderivative of resorcinol {4-(2-pyridylazo)resorcinol (PAR) or 4-(2-thiazolylazo)resorcinol (TAR)}, 2,3,5-triphenyltetrazolium chloride (TTC), water and chloroform. The optimum conditions w.r.t. pH, extraction time, concentration of ADR and concentration of TTC for the extraction of Ga(III) as an ion-associate complex were found.. The composition of the extracted complexes, (TT⁺)[Ga(PAR)₂] (I), (TT⁺)[Ga(TAR)₂] (II) or (TT⁺)₂[Ga(OH)(TAR)₂] (III), and the constants of association (β) between 2,3,5-triphenyltetrazolium cation (TT⁺) with corresponding anionic chelates were established by several methods. The constants of distribution (K_D) and extraction (K_ex) of the principal species I and III were determined as well. The apparent molar absorptivities of the chloroform extract at the optimum extraction-spectrophotometric conditions were ɛ′₅₁₀=9.5×10⁴ L mol⁻¹ cm⁻¹ (I) and ɛ′₅₃₀=4.6×10⁴ L mol⁻¹ cm⁻¹ (III). The validity of Beer’s law was checked and analytical characteristics that were calculated are reported herein.      

Block and graft copolymers based on cationic ring-opening polymerizations

The highly living character of a number of cationic polymerizations has been used to synthesize new, well defined, segmented copolymers. This has been achieved by sequential monomer additions, by grafting reactions, by macromonomer copolymerizations as well as by transfer to polymer. In the present report, a number of examples of such polymers will be presented. The new materials are based on tetrahydrofurane (THF), alkyloxazolines (ROx), cyclic amines, cyclic acetals and cyclic sulfides.     

Nano-Templates from Thermoresponsive Poly(ethoxytriethyleneglycol acrylate) for Polymeric Nano-Capsules

Temperature responsive poly(ethoxytriethyleneglycol acrylate) (PETEGA) of Mn = 8000 and M_w/M_n = 2.30 was synthesized by ATRP. Dilute aqueous solutions of PETEGA exhibit lower critical solution temperature (LCST) at around 34 °C. We found that PETEGA can form nano-sized uniform colloidal aggregates (50-200 nm) above LCST either with or without an additional surfactant. Therefore PETEGA nano-aggregates were used as templates for the seeded free radical copolymerization of acrylamides or methacrylates together with a cross-linker to form acrylamide or methacrylate based core-shell particles. The formation of the PETEGA templates was investigated by dynamic light scattering (DLS) in order to find optimal conditions for obtaining narrow dispersed aggregates of desired sub-micron dimensions. Core-shell particles were characterized by DLS and scanning electron microscopy.     

Styrene–isoprene block copolymers. I. Synthesis and solution properties

Copolymers with a different degree of distribution of styrene and isoprene blocks are prepared by anionic polymerization. The products are characterized by means of ¹H-NMR spectroscopy, GPC, viscometry, and light scattering. The results show that the copolymers are homogeneous in molecular weight and chain composition. In the investigated selective solvents, cyclohexane and base lubricating oil, and equilibrium exists between micelle aggregates and individual polymer coils. The influence of the copolymer structure on the micellization is more pronounced in cyclohexane.     

Characteristics and initiation ability of 9-anthranylmethyl hexafluorophosphate

9-Anthranylmethyl hexafluorophosphate–a stable primary carbenium salt–is prepared and characterized by UV, VIS, and NMR spectroscopy and by conductometric measurements in methylene chloride. 9-Anthranylmethyl hexafluorophosphate initiates the polymerization of vinyl and heterocyclic monomers. This initiator has higher reactivity than trityl and diphenylmethyl salts. The initiation mechanism of the polymerization of some monomers is investigated.     

Macromonomers from vinyl and cyclic monomers prepared by initiation with stable carbenium salts

The initiation of polymerization of α-methylstyrene and p-methoxystyrene with 9-anthranylmethyl salts proceeds by hydride transfer from the monomer to the initiator. As a result, macromonomers with a double bond as head group are formed. These products polymerize and copolymerize by radical and ionic mechanism leading to graft and block copolymers. Styrene and α-caprolactone polymerize with the same initiator by cationation of the monomer. In this case each macromonomer contains one photoreactive anthranylmethyl group which may photodimerize. As a result copolymers of the type A? A or A? B are produced.     

Ternary ion-association complexes between the indium(III) - 4-(2-pyridylazo)resorcinol anionic chelate and some tetrazolium cations

Complex formation and liquid-liquid extraction were studied in systems containing indium(III), 4-(2-pyridylazo)resorcinol (PAR), tetrazolium salt (TZS), water and chloroform. Two different TZS were used: 2,3,5-triphenyl-2H-tetrazolium chloride (TTC) and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT). The optimum conditions for extraction of In(III) as a ternary complex, (TT⁺)[In(PAR)₂] or (MTT⁺)[In(PAR)₂], were found: pH, extraction time, concentration of PAR and concentration of TZS. The constants of extraction (K_ex), constants of association (β), constants of distribution (K_D) and recovery factors (R%) were determined. The apparent molar absorptivities in chloroform were calculated to be ɛ′₅₂₀=6.6×10⁴ L mol⁻¹ cm⁻¹ and ɛ′₅₁₅=7.1×10⁴ L mol⁻¹ cm⁻¹ for the systems with TTC (I) and MTT (II), respectively. Beer’s law was obeyed for In(III) concentrations up to 3.4 μg mL⁻¹ in both the cases. The limits of detection (LOD=0.07 μg mL⁻¹ I and LOD=0.12 μg mL⁻¹ II), limits of quantification (LOQ=0.24 μg mL⁻¹ I and LOQ=0.41 μg mL⁻¹ II) and Sandell’s sensitivities (SS) were estimated as well.      

Copper(II) Complexes of Spirohydantoins. Synthesis,Quantum-Chemical,and Spectroscopic Study

A series of new Cu(II) complexes with important physiologically active cycloalkane-5-spirohydantoines are synthesized reacting as a result of CuCl₂ · 2H₂O interaction with the ligands in alkaline water medium. Their structures were studied using spectroscopic (IR and EPR) methods. For comparison, ab initio calculations of the structure and IR spectra of the corresponding Cu(II) complexes were also performed. It was proven that with cyclopentane-5-spirohydantoins, distorted (flattened) tetrahedral structure is realized Cu(L_–H)₂(H₂O)₂, while with the higher cycloalkane-5-spirohydantoins linear Cu(II) complexes of the type CuL_–H(OH) are formed.