Hyperbranched Polymers

a b s t r a c t 21st Century is treated as the century for highly branched macromolecules, because of their unique structural architecture and outstanding performance characteristics, in the field of polymer science. In the present study, castor oil-based two hyperbranched polyurethanes (HBPUs) were synthesized via A 2 + B 3 approach using castor oil or monoglyceride of the castor oil as the hydroxyl containing B 3 reactant and toluene diisocyanate (TDI) as an A 2 reactant along with 1,4-butane diol (BD) as the chain extender and poly(-caprolactone) diol (PCL) as a macroglycol. The adopted 'high dilution and slow addition' technique offers hyperbranched polymers with high yield and good solubility in most of the polar aprotic solvents. Fourier transforms infra-red spectroscopy (FTIR) and nuclear magnetic resonance (NMR) analyses confirmed the chemical structure of synthesized polymers, while wide angle X-ray diffraction (WXRD) and scanning electron microscope (SEM) resulted the insight of their physical structures. The degree of branching was calculated from 1 H NMR and found to be 0.57 for castor oil based hyperbranched polyurethane (CHBPU), while it was 0.8 for monoglyceride based hyperbranched polyurethane (MHBPU). The studies showed that MHBPU and CHBPU exhibited tensile strength 11 MPa and 7 MPa, elongation at break 695% and 791%, scratch hardness 5 kg and 4.5 kg, gloss 84 and 72, respectively. Thermal properties like thermo stability, melting point, enthalpy, degree of crystallinity and glass transition temperature (T g ); and chemical resistance in different chemical media were found to be almost equivalent for both the polyurethanes. The measurements of dielectric constant and lost factor indicated that both the HBPUs behave as dielectric materials. Thus the synthesized HBPUs have the potential to be used as advanced surface coating materials.

Commercially available Boltorn Hx (xZ20, 30) hyperbranched (HB) polyesters of different theoretical core/monomer ratio (1/12 for H20 and 1/28 for H30) were characterized with respect to molar mass, composition, and structure. The results were compared to those obtained for the Boltorn H40 with a core/monomer ratio of 1/60 [Ž agar E, Ž igon M. Macromolecules 2002;35:9913 [11]]. The main side reaction in the pseudo one-pot synthesis of Boltorn polymers is a self-condensation of bis-MPA leading to the formation of HB structures without a core molecule. These are actually branches containing an unreacted carboxyl group. The fraction of HB structures without a core molecule increases with decreasing core/monomer ratio due to the decreasing fraction of HB structures with a core molecule. Since HB structures without a core molecule are of lower molar masses than HB structures with a core molecule, they particularly decrease the number average molar masses of the samples compared to the theoretically calculated ones. The polydispersity of Boltorn Hx increases with decreasing core/monomer ratio. Some of the hydroxyl groups were found to react intramoleculary forming ether bonds. Boltorn Hx polyesters have low degrees of branching due to the limited carboxyl group conversions, low DP n values, the presence of the core unit, and lower reactivity of hydroxyl groups in linear repeat units compared to those in terminal ones. The degree of branching according to Frey increases with decreasing core/monomer ratio. q

In the present study, a high performance, tough, antimicrobial, hyperbranched epoxy nanocomposite is fabricated by the incorporation of neem oil-immobilized organo-modified montmorillonite nanoclay. The immobilization of neem oil with organo-modified montmorillonite nanoclay is performed by the combined effect of mechanical and ultrasonic forces under ambient conditions. This immobilization is confirmed by FTIR and XRD studies. FTIR, XRD, SEM and TEM analyses also confirm the formation of the exfoliated nanocomposite. The dose-dependent enhancements of tensile strength (50%), elongation at break (3-fold), toughness (5.5-fold) and thermal stability (20 1C) of the pristine epoxy thermoset are observed for the nanocomposite. Antimicrobial studies are performed by growth curve and zone-ofinhibition analyses against different bacteria and a fungus at different doses of neem oil-immobilized organo-modified montmorillonite nanoclay. The nanocomposite with 50 wt% neem oil-immobilized organo...

Dendritic polymers (dendrimers and hyperbranched polymers) are becoming increasingly popular due to their vast range of uses. Due to their distinctive and novel qualities, they have demonstrated a strong interest. Since its discovery, dendritic polymers have become a potential material for many research applications, ranging from biomedical and tissue engineering to catalytic and energy applications. Since then, dendritic polymers’ unique features have become a promising platform for a variety of uses. Dendritic polymers have made great progress in overcoming basic and technological problems related to their biomedical and energy applications. This review summarizes the strategies of synthesizing dendrimers and hyperbranched polymers. Further, the review highlights the applications of dendrimers and hyperbranched polymers in many study fields such as drug delivery, gene delivery, tissue engineering, catalysis, and energy storage. This review concludes with future avenues to be explored for the applications of dendritic polymers.