Hydroxylated hyperbranched polyesters as crosslinking agents for polyurethane networks: Partial modification of the OH chain ends

Synthesis and Properties of Nitrogen Heterocycle-Functionalized Core-Shell Hyperbranched Polyester

Core-shell hyperbranched polyesters (HBPE) of third generation prepared from 2,2′-bis (hydroxymethyl) propionic acid (Bis-MPA) as an ABx monomer and N-heterocyclic (indole, piperidine and piperazine) phosphoryl dichloride as a core molecule by melt condensation process. These polymers were characterized by FT-IR, 1H NMR, 13C NMR, 31P NMR, elemental analysis, and MALDI spectroscopy. The thermal behavior of the polymers has been investigated by thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC). There is no weight loss observed until 250 °C under nitrogen atmosphere. DSC showed that the glass transition temperatures was about −14 and −30 °C for the prepared core-shell HBPE. The dielectric properties such as dielectric constant and loss factor for these polyesters were also studied with respect to change of frequency (50 Hz to 5 MHz).

Synthesis and characterization of novel hydroxyl-terminated hyperbranched polyurethanes

A series of novel hydroxyl-terminated hyperbranched polyurethanes (HBPUs) were synthesized via stepwise polymerization by diethanolamine (DEOA), isophorone diisocyanate (IPDI) and trimethylolpropane (TMP). It is interesting to note that the HBPUs can be purified by water. The HBPUs were characterized with 1H nuclear magnetic resonance (NMR), 13C NMR, Fourier transform infrared spectroscopy (FT-IR) and elemental analysis. The average degree of branching (DB) of HBPUs was calculated from the first generation to the fourth generation to be 1.00, 0.74, 0.59 and 0.57 by quantitative 13C NMR, respectively. The branching model and molecular structure of HBPUs were deduced by the 13C NMR and the value of DB. To investigate the changes of hydrogen bonding interaction in HBPUs with a variation in structure of different generations, the deconvolution of FT-IR spectra was carried out using Origin 7.0 software through the Gaussian curve-fitting method. The ratio of hydrogen-bonded -NH and -OH groups of HBPUs was calculated to be 80.8%, 85.1%, 84.8% and 85.4% from the first generation to the fourth generation by deconvoluted -NH and -OH zone, respectively. The interaction of hydrogen bonding and glass transition temperature (Tg) of HBPUs increased with the increase of generation. The trend of thermal stability and Tg coincide with the change of hydrogen-bonded interactions.

Dielectric properties of castor oil cross-linked polyurethane

A series of polyurethanes cross-linked with castor oil were synthesized and the influence of the polyurethane chemical structure on molecular relaxations in such systems was determined. Three different castor oil rates were used in the synthesis of the cross-linked polyurethane chains. These cross-linked polyurethanes were compared with a linear polyurethane which was obtained by chain extension with 1,4-butane diol. The dielectric properties and relaxation phenomena of the polyurethane were studied as a function of the hard segment structure and cross-linker content as structural variables and frequency and temperature as experimental variables. It was found that the formation of hydrogen bonds between urethane groups of physical networks may control the molecular mobility, but the chemical nature and content of the cross-links of the hard segments strongly influences the molecular relaxation. The relaxation peaks were observed in the temperature range of -65 to 60°C for polyurethane with different cross-linked segment contents, peaks which shifted to high temperature with the increase in frequency.

Crosslinked polyurethanes based on hyperbranched polymers

In this paper, two samples of polyurethane (PU) crosslinked with hydroxy -functonal hyperbranched aliphatic polyester of the second pseudo generation were investigated. For the synthesis of these crosslinked PUs two different macrodiols were used: poly(tetramethyleneoxide) (PTMO) for PUPTMO and ethylene oxide-poly(dimethylsiloxane)-ethylene oxide (PDMS-EO) for PUPDMS-EO sample. Synthesized samples behave as elastomers and have yellow color. Obtained results show that swelling degree of the sample PUPDMS-EO in N-methyl-2-pyrrolidinon (NMP) determined at room temperature is higher than for the sample PUPTMO. It has been also observed that thermal properties of these polyurethane networks can be changed by incorporation of siloxane sequences in their structure.