Spectroscopic investigation of polystyrene surface grafting on natural rubber

This paper investigates the structural characteristics of polystyrene (PS) grafted on a natural rubber (NR) surface using Raman scattering spectroscopy. The nitroxide-mediated radical polymerization (NMRP) technique was used to achieve the graft copolymerization of PS onto the surface of NR film using 2,2,6,6-tetramethyl-l-piperidinyIoxy (TEMPO) as a nitroxide mediator. The reversible reaction between propagating radical and TEMPO of the NMRP process leads to a controlled radical polymerization of styrene on the NR surface. The grafting degree of PS on the NR was first measured by gravimetric methods. It was found to depend linearly on the grafting time. The characteristic signals detected by Raman scattering and by attenuated total reflection (ATR) Fourier transform infrared (FT-IR) spectroscopy provide clear evidence of the PS being grafted onto the NR. The distribution of the grafted PS on the NR substrate was determined from the Raman mapping. It is seen that the grafting occurs homogeneously over the entire surface (∼40 mole % PS). The study using the Raman depth profiling technique on the original sample compared with the analysis carried out on the sample prepared by cross-sectioning led to important and comparable information regarding the uniform distribution of PS grafting inside the substrate.