Title of article :
Graft Copolymerization of Styrene onto Poly(vinyl alcohol) Initiated by Potassium Diperiodatocuprate(III)
Author/Authors :
Bai, Libin Hebei University - College of Chemistry and Environmental Science, China , Wang, Chunyan Hebei University - College of Chemistry and Environmental Science, China , Jin, Jia Hebei University - College of Chemistry and Environmental Science, China , Liu, Yinghai Hebei University - College of Chemistry and Environmental Science, China
From page :
847
To page :
855
Abstract :
The graft copolymerization of styrene (St) onto poly(vinyl alcohol) (PVA) is studied by using a novel redox system of potassium diperiodatocuprate-PVA (Cu(III)- PVA) in alkaline medium. Cu(III)-PVA redox pair is an efficient initiator for this graft copolymerization which is proved by high graft efficiency ( 97%) and high percentage of graft ( 300%). Reaction conditions (monomer-to-PVA weight ratio, initiator concentration, pH, time and temperature) affect the graft parameters which have been investigated systematically. The optimum reaction conditions are found as St/PVA = 5.4; [Cu(III)] = 1×10-2 M; pH = 12.7; temperature = 50؛C; time = 3.5 h. Further, the equation of the overall polymerization rate can be written as follows: Rp = k C1.9 (St) C1.7 (Cu(III)). The overall activation energy was calculated to be 42.0 kJ/mol based on the experimental data of the relations between Rp and C(St); Rp and C(Cu(III)); and Rp and temperature. A mechanism is proposed to explain the formation of radicals and the initiation. The structure of the graft copolymers is confirmed by Fourier transfer infrared spectroscopy (FTIR). Some peaks were compared with PVA at 3080.34-3001.79 cm-1 (=C-H stretching in the phenyl ring), 1600.34-1450.95 cm-1 (C=C stretching in the phenyl ring), 755.17 cm-1 and 698.64 cm-1 (=C-H out-off-plane bending in phenyl ring) which are considered to belong to the characteristic absorption bands of phenyl group of polystyrene. Therefore it proves that the graft copolymer is composed of PVA and PSt. TGA thermograms of PVA and PVA-g-PSt are investigated as well. As it is shown the initial decomposition temperature of PVA-g-PSt (377.3؛C) is much higher than that of PVA (241.8؛C), which indicates that the thermal stability of the PVA is obviously enhanced by grafting with PSt. X-Ray diffraction elucidates the incorporation of PSt with PVA which reduces the crystal degree of PVA.
Keywords :
potassium diperiodatocuprate , poly(vinyl alcohol) , styrene , graft copolymer , redox system.
Journal title :
Iranian Polymer Journal
Journal title :
Iranian Polymer Journal
Record number :
2583870
Link To Document :
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