The polymer brush technology based on grafting to from melt involves the preparation of an ultrathin film of some tens of nanometers placed on the substrate surface, followed by a grafting reaction to promote the grafting to process. Since the grafting to reaction is a self-limiting reaction a homogeneous and highly reproducible brush is expected to be obtained with enormous implications for proper integration of this technology into industrial production lines. Within this frame, it is to be observed that in the grafting to process, the structure and molecular weight characteristics of the grafted layer are generally, but implicitly, believed to precisely reflect the characteristics of the starting polymeric material. However, it was recently demonstrated that some discrimination by molecular weight takes place during the grafting to process from solution, with shorter chains being preferentially attached to the substrate. As the molecular weight of the polymer chains grafted to the surface is the most important parameter that controls the thickness of the brush layer and the properties of the newly prepared surface, the assessment of the actual molecular weight and distribution of the grafted chains is of outmost relevance not only to shed light into the grafting to mechanism but also in the view of the industrial applications of this technology.
The present contribution addresses the quantification of the molecular weight of grafted chains by performing the grafting reaction with model blends consisting of fully hydrogenated and partly deuterated statistical copolymers with the appropriate molecular weights and distributions. As TGA-GC-MS can easily distinguish and quantify the styrene and deuterated styrene that evolve during the TGA heating step, a direct measurement of the grafted layer composition is obtained from which the average molecular weight of the polymers forming the brush can be calculated. A precise picture of the effect of the molecular weight on the grafting to reaction will be reported.

Grafted deuterated copolymer with a hydrogenated copolymer layer on top

michele laus

university east piemonte

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