Structural and Thermal Properties of Ethylene-Norbornene Copolymers Obtained Using Vanadium Homogeneous and SIL Catalysts

The series of ethylene-norbornene (E-NB) copolymers was obtained using different vanadium homogeneous and supported ionic liquid (SIL) catalyst systems. The 13C and 1H NMR (carbon and proton nuclear magnetic resonance spectroscopy) together with differential scanning calorimetry (DSC) were applied to determine the composition of copolymers such as comonomer incorporation (CNB), monomer dispersity (MD), monomer reactivity ratio (re), sequence length of ethylene (le) and tetrad microblock distributions. The relation between the type of catalyst, reaction conditions and on the other hand, the copolymer microstructure, chain termination reaction analyzed by the type of unsaturation are discussed. In addition, the thermal properties of E-NB copolymers such as the melting and crystallization behavior, like also the heterogeneity of composition described by successive the self-nucleation and annealing (SSA) and the dispersity index (DI) were determined.

Copolymerization of D,L-lactide and ε-caprolactone using tin(II) octanoate as catalysts: an insight into copolymer microstructure

Sn(Oct)2-catalyzed ring-opening copolymerization of D,L-lactide and e-caprolactone in bulk at 130 °C at different D,L-lactide/e-caprolactone has been studied. It was shown that independent on the initial comonomers ratio, the synthesized copolymers are enriched by D,L-lactide at the early stage of reaction indicating the formation of gradient-like copolymer. However, the intensive transesterification reaction both during the polymerization and at the monomer-starved conditions leads to the redistribution of the monomer sequences and formation of the random copolymer. The synthesized copolymers are characterized by high polydispersity (Đ > 2.0), which raises when the reaction mixture was kept under monomer-starved conditions that confirms the occurrence of transesterification. The formation of random copolymer is confirmed by single Tg value, which gradually increased with the increase of the amount of D,L-lactide in the copolymer from –48.6 °C to 33.3 °C for D,L-lactide/e-caprolactone ratio in copolymer of 20:80 and 90:10 mol/mol, respectively.

Morphological and Spectral Analysis of Polystyrene-Block-Polyisoprene-Poly(Butyl Acrylate) Triblock Copolymer

Polystyrene-block-polyisoprene-block-poly (butyl acrylate) or PS-b-PI-b-PBA triblock copolymer with different ratio (5:5 and 4:6) of styrene and isoprene unit have been synthesized by anionic polymerization. The product had been characterized by using Scanning Electron Microscopy (SEM) and N-Nuclear Magnetic Resonance (H-NMR). The results of SEM images reveal that more rubber matrix can be seen for 4:6 ratios as compared to 5:5 ratios due to high content of isoprene in the copolymer. H-NMR results indicate that the peaks of polystyrene, polyisoprene and butyl acrylate for ratio 5:5 exists at 6.50 – 7.28 ppm, 4.68 – 4.88 ppm, and 0.80 – 1.83 ppm. As for ratio 4:6, the peaks can be observed at 6.30 – 7.33 ppm, 5.19 – 5.70 ppm, and 1.18 – 1.78 ppm respectively. The H-NMR analysis of the copolymer microstructure confirms that both copolymer are primarily consists of polystyrene, polyisoprene and polybutyl acrylate segment.