Long　chain　branched　polypropylene　random　copolymers　(LCB-PPRs)　were　prepared　via　reactive　extrusion　with　the　addition　of　dicumyl　peroxide　(DCP)　and　various　amounts　of　1,6-hexanediol　diacrylate　(HDDA)　into　PPR.　Fourier　transform　infrared　spectrometer　(FTIR)　was　applied　to　confirm　the　existence　of　branching　and　investigate　the　grafting　degree　for　the　modified　PPRs.　Melt　flow　index　(MFI)　and　oscillatory　shear　rheological　properties　including　complex　viscosity,　storage　modulus,　loss　tangent　and　the　Cole-Cole　plots　were　studied　to　differentiate　the　LCB-PPRs　from　linear　PPR.　Differential　scanning　calorimetry　(DSC)　and　polarized　light　microscopy　(PLM)　were　used　to　study　the　melting　and　crystallization　behavior　and　the　spherulite　morphology,　respectively.　Qualitative　and　quantitative　analyses　of　rheological　curves　demonstrated　the　existence　of　LCB.　The　effect　of　the　LCB　on　crystalline　morphology,　crystallization　behavior　and　molecular　mobility,　and,　thereby,　the　mechanical　properties　were　studied　and　analyzed.　Due　to　the　entanglements　between　molecular　chains　and　the　nucleating　effect　of　LCB,　LCB-PPRs　showed　higher　crystallization　temperature　and　crystallinity,　higher　crystallization　rate,　more　uniformly　dispersed　and　much　smaller　crystallite　compared　with　virgin　PPR,　thus　giving　rise　to　significantly　improve　impact　strength.　Moreover,　the　LCB-PPRs　exhibited　the　improved　yield　strength.　The　mobility　of　the　molecular　chain　segments,　as　demonstrated　by　dynamic　mechanical　analysis　(DMA),　was　improved　for　the　modified　PPRs,　which　also　contributed　to　the　improvement　of　their　mechanical　properties.　©　2016,　Chinese　Chemical　Society,　Institute　of　Chemistry,　Chinese　Academy　of　Sciences　and　Springer-Verlag　Berlin　Heidelberg.