Grafting

Abstract: Graft copolymers of a water soluble monomer and polysaccharide are prepared employing a two-phase reaction system under controlled conditions. The resultant graft copolymers are formed at high grafting efficiency and high conversion and obtained as precipitated solid beads.

Abstract: Single-layer graphene nanosheets (SLGNs) are prepared by reduction of well-exfoliated graphite oxide aided by a surfactant (sodium dodecylbenzene sulfonate, SDBS). Grafting density and polystyrene (PS) chain lengths are controlled by modulating the concentrations of diazonium compound and monomer during the grafting reaction of the initiator and the succeeding atomic transfer radical polymerization (ATRP). Atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectra and transmission electron microscopy (TEM) are used to confirm the single-layer structure of graphene sheets, covalent bonding at the interface, and distribution uniformity of grafting PS chains at the SLGN surface. Thermogravimetric analysis (TGA) is performed to assess the control of grafting density and chain length. PS chains grafted on the SLGN surface exhibited remarkably confined relaxation behavior. An increase in the glass transition temperature (Tg) of up to 18 °C is observed for high grafting density, low molecular weight polymer-grafted graphene samples. The low grafting density, high molecular weight sample shows an increase in Tg of ∼9 °C, which is attributed to superior heat conduction efficiency. The measured thermal conductivity for the PS composite film with 2.0 wt% SLGNs increase by a factor of 2.6 compared to that of the pure PS.

Abstract: With the aim of determining whether grafting could improve salinity tolerance of tomato (Lycopersicon esculentum Mill.), and what characteristics of the rootstock were required to increase the salt tolerance of the shoot, a commercial tomato hybrid (cv. Jaguar) was grafted onto the roots of several tomato genotypes with different potentials to exclude saline ions. The rootstock effect was assessed by growing plants at different NaCl concentrations (0, 25, 50, and 75 mM NaCl) under greenhouse conditions, and by determining the fruit yield and the leaf physiological changes induced by the rootstock after 60 d and 90 d of salt treatment. The grafting process itself did not affect the fruit yield, as non-grafted plants of cv. Jaguar and those grafted onto their own root showed the same yield over time under non-saline conditions. However, grafting raised fruit yield in Jaguar on most rootstocks, although the positive effect induced by the rootstock was lower at 25mMNaCl than at 50 and 75mM NaCl. At these higher levels, the plants grafted onto Radja, Pera and the hybrid Volgogradskij3Pera increased their yields by ~80%, with respect to the Jaguar plants. The tolerance induced by the rootstock in the shoot was related to ionic rather than osmotic stress caused by salinity, as the differential fruit yield responses among graft combinations were mainly related to the different abilities of rootstocks to regulate the transport of saline ions. This was corroborated by the high negative correlation found between fruit yield and the leaf Na1 or Cl2 concentrations in salt-treated plants after 90 d of salt treatment. In conclusion, grafting provides an alternative way to enhance salt tolerance, determined as fruit yield, in the tomato, and evidence is reported that the rootstock is able to reduce ionic stress.