## 1 Introduction  
As is well known, the importance of polypropylene (PP) cannot be over complimented in the modern world [1; 2]. With great effort over decades, substantial progress has been made to meliorate the weaknesses of this material, but these have still been far from satisfactory until now. Modification in the polymerization process has proven to be successful in the preparation of PP in reactor alloys [3]; whereas, due to the limitations of the intrinsic nature of the Ziegler-Natta catalyst, the preparation of PP with a branched structure, and that with non-\(\alpha\)-olefinic monomers such as sytrenic and polar monomers incorporated in the main chain, tends to be extremely difficult by directly using the polymerization process. Therefore, post-polymerization reactions are considered to be more practical and have been extensively studied [4].  
Chlorination of polyolefin by using the reaction of polyolefin nascent particles with chlorine gas in water media is an easy and economical way to obtain functionalized polyolefin materials due to the inexpensive and excess chlorine gas resource resulting from the chlor-alkali industry. Chlorinated polyethylene (CPE) and chlorinated polyethylene rubber (CM) have been commercialized in large capacity since the materials have been endowed with excellent weather fastness, flame retardancy, and elastomeric properties by chlorination [5]. However, chlorinated PP (CPP) still has problems to be a useful material since the thermo-instable C-Cl bond cannot be sustained at the processing temperature of crystalline PP chain segments (normally, over 170 \({}^{\circ}\)C), giving rise to the release of unpleasant corrosive HCl gas accompanied by severe molecular weight decline [6]. From our viewpoint, the C-Cl bond can be employed as a reaction site for organic substitution reaction to convert the chlorine atom to a thermally-stable organic group and to open up a way to enrich the polyolefin material family and expand the applications as an expectation.  
Herein, we attempted to synthesize polypropylene with sytrenic monomer units incorporated in the main chain by using the Friedel-Crafts alkylation reaction between CPP and substituted benzene as raw materials together with the Lewis acid as the catalyst. Although the Friedel-Crafts alkylation reaction using CPP as a component has been reported for the preparation of in situ compatibilized PP-based polymer blends [7], it has not been reported yet as a pathway for the synthesis of polypropylene with sytrenic monomers incorporated in the backbone and utilization as a compatibilizer for PP/PS blends. As a combination of two major polymeric materials, PP/PS blends are undoubtedly of great scientific and commercial interest. Although various commercial compatibilizers such as PP graft maleic anhydride (PP-\(g\)-MAH), Polystyrene-\(b\)-poly(ethylene-\(r\)-butylene)-\(b\)-polystyrene (SEBS), Surlyn, etc. have been reported for compatibilization of PP/PS blends [8; 9], the compatibilization efficiencies of those compatibilizers cannot be well complimented due to insufficient structural similarity. It is interesting from a scientific aspect that a well-defined polypropylene-_graft_-polystyrene synthesized by a two-step polymerization process and used as compatibilizer for PP/PS blend have been reported [10].  
In this work, a series of propylene-_co_-styrene monomer copolymers were synthesized by using the Friedel-Crafts alkylation reaction, and those copolymers as a compatibilizer for the PP/PS blend were investigated by using the impact test, morphology observation, dynamic mechanical analysis, thermo- and rheological behavior measurements.