Preparation Of Imidization Products Of PS-b-(alt) SMA And Application As Pour Point Depressant For Crude Oil

Styrene (St) and Maleic anhydride (MAh) copolymers (SMA) can be imidized by amine due to the reactivity of anhydride group. In this work, polystyrene-b-poly(styrene-alt-maleic anhydride) (PS-b-(alt)SMA) with well-defined structures have been prepared using reversible addition-fragmentation chain transfer (RAFT) polymerization technique in three different approaches. Sequentially, thease PS-b-(alt)SMA are imidized and the imidization products is used as pour point depressants. The aim is to investigate the effects between polymer structures and actions as pour point depressant for crude oil.-b-(alt)SMA, have been prepared by RAFT polymerization technique using three different approaches:1-phenylethyl phenyldithioacetate(PEPDTA) directly as RAFT agent, polystyrene (PS) block as the macromolecular PS-RAFT agent and poly(styrene-maleic anhydride) (SMA) block with alternating sequence as the macromolecular SMA-RAFT agent. It has been found that well-defined PS-b-(alt)SMA with narrow molecular weight distribution (MWD) and strict alternate structure in SMA block can only be obtained using the PS-RAFT agent. A series ofPS-b-(alt)SMA with various well-defined chain structure are imidized with octadecyl amine. Ring-opening reactions between PS-b-(alt)SMA and octadecyl amine are taken place at room temperature to prepare Polystyrene-block-poly (styrene-alt-N-octadecyl maleamic acid)(PS-b-(alt)SNODMA). Polystyrene-block-poly (styrene-alt-N-octadecyl maleimide)(PS-b-(alt)SNODMI) are synthesized by ring-closing reaction of PS-b-(alt)SNODMA at 120℃. The structures of products are comfirmed by spectra of Fourier transform infrared spectrometer(FTIR). PS-b-(alt)SNODMI with different structures are used as pour point depressants for model waxy oil(4%wtC24 or C36 as paraffin in decane). Differential Scanning Calorimeter(DSC), polarizing microscope with hot stage and rotation rheometer are employed to characterize the model waxy oil with PS-b-(alt)SNODMI dissolved in them.According to DSC results and morphology photos of crystal in decane taken from polarizing microscope, PS-b-(alt)SNODMI can decrease crystalization temperature(Tc) and melting temperature(Tm) for C24 as paraffin in model waxy oils. However, for C36 as paraffin in model waxy oil, decreases in Tc and Tm are not significant. The size of wax crystal will get smaller and more dispersed in model oils for all PS-b-(alt)SNODMI samples. With the increase of Mn of PS-b-(alt)SNODMI or Mn of (alt)SNODMI block, wax crystal become smaller and more dispersed. From rheology results, PS-b-(alt)SNODMI as pour point depressants for the model waxy oils can decrease complex viscosity (η*) and yield stress (τy) of the model waxy oils. For the system with C24 as paraffin,η* can be reduced by more than an order of magnitude andτy can be reduced by 70%. PS-b-(alt)SNODMI with total Mn 9600 or (alt)SNODMI block Mn of 4500 result in the minimumη* andτy. However, for the model waxy oils with C36 as paraffin,η* andτy will be decreased but to a less extend. Polymers with longer PS-b-(alt)SNODMI or with longer (alt)SNODMI block in PS-b-(alt)SNODMI have more effects on C36 system.