• Polymer(Korea)
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• v.39 no.1
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• pp.180-184
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• 2015

PP-grafted GO was prepared by the reaction of graphene oxide (GO) containing 2-bromoisobuyryl groups and polypropylene (PP) having hydroxyl groups (PP-OH) via a "grafting-to" method. GO-Br was synthesized by the reaction of GO and 2-bromoisobutyryl bromide under a basic condition. PP-MAH was reacted with ethanolamine to produce PP-OH. The melting temperature of PP-grafted GO was shifted to the higher temperature than that of PP-OH. Also, the thermal stability of PP-grafted GO was increased as compared to PP-OH and GO. These results demonstrated that the grafted coating polymer PP was effective for enhancing the thermal stability of GO. The higher surface roughness of PP-grafted GO was resulted from the chemical attachment of PP on the surface of GO. The characterization of PP-grafted GO was conducted from Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscope (SEM).

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.11a
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• pp.90-90
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• 2012

Catechol moiety has enough reducing capability of reducing metal ions. Catechol-grafted polymer is chemically synthesized and electrospun into nanofibers as templates for metal nanostructures. The metal nanostructures are spontaneously generated on the catechol-grafted polymer nanofibers under ambient conditions.

• Polymer(Korea)
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• v.36 no.5
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• pp.656-661
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• 2012

The palladium nanoparticles were self-assembled to make Pd-POSS using POSS-$NH_3{^+}$ (polyhedral oligomeric silsesquioxane) as a crosslinker. Graphene oxide (GO) was produced by the reaction of graphite under a strong acid and oxidizer and poly(acrylic acid) (PAA) was covalently grafted on the surface of graphene to make PAA-grafted graphene through the radical polymerization of acrylic acid and GO along with a reduction process under $NaBH_4$. The nanocomposites of Pd-POSS and PAA-grafted graphene were fabricated via ionic interactions between positively charged Pd-POSS and negatively charged PAA-grafted graphene. Pd-POSS nanoparticles were attached to the surface of PAA-grafted graphene through ionic interactions. The thermal stability of Pd-POSS/PAA-grafted graphene was higher than that of PAA and PAA-grafted graphene. The composition, structure, surface morphology, and thermal stability of the Pd-POSS/PAA-grafted graphene were studied by FE-SEM, AFM, TEM, FTIR, and TGA.

• Macromolecular Research
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• v.15 no.1
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• pp.51-58
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• 2007

The approach studied in the present work produced an exfoliated state of clay layers via confinement of the charged nano-sized polystyrene (PS) beads within the gallery of swollen pristine clay. It was demonstrated that adsorption of the polymer nanobeads dramatically promotes expansion of the clay gallery. A comparative study of incorporation was conducted by employing organo-modified clay along with two different colloid polymer systems: electrostatically stabilized PS nanobeads and cationic monomer-grafted PS nanobeads. The mechanism of adsorption of the monomer-grafted polymer beads onto clay via cationic exchange between the alkyl ammonium group of the polymer nanobeads and the interlayer sodium cation of the layered silicate was verified by using several techniques. As distinct from the polymer nanobeads formed using conventional miniemulsion polymerization method, competitive adsorption of stabilizing surfactant molecules was be prevented by grafting the surface functional groups into the polymer chain, thereby supporting the observed effective adsorption of the polymer beads. The presence of surface functional groups that support the establishment of strong polymer-clay interactions was suggested to improve the compatibility of the clay with the polymer matrix and eventually play a crucial role in the performance of the final nanocomposites.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.6.2-6.2
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• 2011

Block copolymer (BCP) self-assembly in a film geometry has recently been the focus of increased research interest due to their potential use as templates and scaffolds for the fabrication of nanostructured materials. The phase behavior in a thin film geometry that confines polymer chains to the interfaces will be influenced by the interfacial interactions at substrate/polymer and polymer/air and the commensurability between the equilibrium period (L0) of the BCP and the total film thickness. We investigated the phase transitions for the films of block copolymers (BCPs) on the modified surface, like the order-to-disorder transition (ODT) by in-situ grazing incidence small angle x-ray scattering (GISAXS) and transmission electron microscopy (TEM). The selective interactions on the surface by a PS-grafted substrate provide the preferential interactions with the PS component of the block, while a random copolymer (PS-r-PMMA) grafted substrate do the balanced interfacial interactions on the surface. The thickness dependence of order-to-disorder behavior for BCP films will be discussed in terms of the surface interactions.

• Journal of the Korean Chemical Society
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• v.34 no.2
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• pp.197-202
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• 1990

Polyethylene glycol (PEG) grafted poly γ-benzyl L-glutamate (PBLG) were prepared from esterification or substitution reaction of PBLG with PEG having hydroxyl group at one end or primary amino groups at both ends. The viscosity of these polymer solution was decreased with decrease of polymer concentration. But in more dilute solution the viscosity was increased with decrease of polymer concentration. PEG-grafted PBLG polymers showed smaller water contact angles than PBLG homopolymer, and the water contact angles of the surface of PEG-grafted PBLG polymers were largely dropped by reacting with aminoethanol, resulting in hydrogel surfaces.

• Polymer(Korea)
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• v.38 no.3
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• pp.378-385
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• 2014

Multiwall carbon nanotubes (MWCNTs) were modified with a water soluble polymer, poly(vinyl alcohol), PVA, using a simple ultrasonic wave in water. Under the irradiation of ultrasound, PVA chains were severed as macroradicals and instantly grafted onto the surface of MWCNTs due to the radical scavenging effect of MWCNTs. To control the grafting PVA onto MWCNTs, the ultrasonication power and irradiation time were changed from 300 to 500 W and from 10 to 50 min, respectively. The grafted PVA onto MWCNTs was confirmed by FTIR, TGA, SEM, and TEM. Dispersion stability of the modified MWCNTs was monitored by Turbiscan. The amount of grafted PVA on MWCNTs increased with the increase in the sonication power and irradiation time. The grafted PVA on MWCNTs induced the improved dispersion stability of the modified MWCNTs in water. These findings exhibit that ultrasound can be readily used for the grafting polymer chains on MWCNTs.

• Polymer(Korea)
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• v.26 no.2
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• pp.279-286
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• 2002

For surface modification of polymers with hydrophilic functional groups, acrylic acid was grafted and immobilized on the surface of polyethylene(PE) by cold-plasma treatment using Ar gas. The modifications were identified by analysis of ATR-IR spectrum and by the measurement of contact angles. Compared to virgin PE significant decreases in contact angle were observed for both the grafted PE and the immobilized PE. The decreases of contact angle were in the range of 47~$53^{\circ}$ for grafted PE and 23~$26^{\circ}$ for immobilized PE. The degree of hydrophilicity depended strongly on the plasma-treating time and discharge power. For the case of grafting it has show that the longer plasma-treating time, the higher hydrophilic character. For the case of immobilization, whereas, higher discharge power and longer exposure to plasma have shown the detrimental effect for the preparation of hydrophilic PE surface due to the decrease of carboxyl group by ablation effect. The decrease in adhesion strength of immobilized PE. compared to grafted PE, was also attributed to the ablation of carboxyl group.

• Elastomers and Composites
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• v.47 no.2
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• pp.162-167
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• 2012

Surface modification of macromolecules renders a progressive and favorable method to enhance the properties of polymeric materials and improves conductivity, wettability, stability, adhesion, antibacterial properties, etc. of polymeric surfaces without deterioration of the polymer bulk properties. Polyolefins such as polyethylene and polypropylene were grafted with maleic anhydride(MAH) as a functional monomer in solution. Evidence for grafting was shown with FTIR measurement. The grafting ratio was determined from chemical titration. The higher MAH loading, the lower contact angle(${\theta}$) was obtained. With the increasing content of MAH, melting temperature($T_m$) of maleic anhydride grafted polymer decreased while decomposition temperature($T_d$) of maleic anhydride grafted polymer increased.

• Polymer(Korea)
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• v.32 no.4
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• pp.359-365
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• 2008

We have fabricated a novel thermo-responsive nanofibrous surfaces by grafting PIPAAm by electron beam irradiation onto poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV) nanofibrous mats. The electrospun PHBV nanofiber structures revealed randomly aligned fibers with average diameter of 400 nm. Increased atomic percent of nitrogen was observed on the PIPAAm-grafted PHBV mats after electron beam irradiation determined by ESCA. The amounts of PIPAAm-grafted onto PHBV films were $6.49{\mu}g/cm^2$ determined by ATR-FTIR. The PIPAAm-grafted surfaces exhibited decreasing contact angles by lowering the temperature from 37 to $20^{\circ}C$, while ungrafted PHBV surfaces had negligible contact angle change. This result indicates that PIPAAm surfaces, which are hydrophobic at the higher temperature, became markedly more hydrophilic in response to a temperature reduction due to spontaneous hydration of the surface-grafted PIPAAm. Thermo-responsive nanofibers showed good tissue compatibility. Cultured cells were well detached and recovered from the surfaces by changing culture temperature from 37 to $20^{\circ}C$.