For the synthesis of an NTBA-MA copolymer, various molar ratios of NTBA and MA were dissolved in p-dioxane in a round-bottom flask equipped with a magnetic stir bar and in a thermostated silicon oil bath at 65 [+ or -] 0.1[degrees]C and a nitrogen inlet.
To the determine the monomer reactivity ratios, the copolymerization of NTBA with MA using various monomer feed ratios was carried out in p-dioxane by free radical copolymerization in the presence of AIBN as an initiator in nitrogen inlet.
The copolymer compositions were found by elemental (N content for NTBA units) and chemical (acid number for anhydride units) FTIR and [sup.1]H NMR spectroscopy using an integral area of chemical shifts of monomer functional groups for quantitative analysis.
The absorption value ratios between characteristic analytical bands of 1658 [cm.sup.-1] (for band in NTBA unit), 1775 [cm.sup.-1] (for C=O band in MA unit) and the least changing absorption band of 1365 [cm.sup.-1] as a standard band (A = log(I/[I.sub.o]), [DELTA][A.sup.i] = [A.sup.i]/[A.sup.1365]) were used to calculate the copolymer composition.
where [M.sub.1] and [M.sub.2] are molecular weights of NTBA and MA monomer units, respectively.
The compositions of the copolymers synthesized were determined by comparing the integrals of the tert-butyl and methyne group regions in the spectra of NTBA and MA units, respectively.
The grafting degree of NTBA was determined with nitrogen analysis of the purified samples for a minimum of two samples.
The intensities of the new peaks increased with the increase of NTBA in the grafting content.
The initial concentrations of peroxide initiator and monomer affected grafting content of NTBA on PP, and the results are illustrated in Figs.
The grafting content of NTBA onto PP varied from 50 to 150 mpm depending on the initial concentration of the monomer, peroxide, and comonomer.
In the sample of the copolymer with St (NTBA-co-S2), in addition to NTBA characteristic peaks at 1660 and 1550 [cm.sup.-1], new absorption peaks at 1603 and 702 [cm.sup.-1] were observed, which can be assigned to the absorption of the phenyl ring of St.
The effect of St on grafted efficiency can be observed by increase of concentration ratios of St to NTAB on grafted NTBA contents on PP, shown in Fig.