Study On Polytetrafuran And Its Piperazine Extended Polyether Urethane

Polyurethane(PUs)is a kind of copolymers composed of soft and hard segments.The phase separation between soft and hard segments is the structural basis of PU to demonstrate excellent performances.Polytetramethylene ether glycol(PTMEG)is flexible with high crystallinity and piperazine(PPZ)is cyclic secondary diamine.We hypothesized that the formed polyether PU with PTMEG as soft segments and PPZ as chain extender may become a new PU with enhancing phase separation and good biosafety.On the other hand,for the industrial preparation of PTMEG,solid superacids are often employed to catalyze the ring-opening polymerization of tetrahydrofuran(THF),which are featured with high recyclability and low equipment corrosion.Unfortunately,almost all the solid superacids industrially applied in China are imported.Accordingly,development and screening of a solid superacid that is comparable to those imported ones are essentially urgent and important to facilitate the localization of PTMEG production technologies.In this study,the catalystic effects of a home-made solid superacid,fluorinated sulfonic acid resin(Catalyst B)was detected and evaluated by using an imported fluorinated sulfonic acid resin(Catalyst A)as the control.And then PTMEG as soft segment,hexamethylene diisocyanate(HDI)as couping agent and PPZ as chain extender were employed to synthesize a new polyether PU(PTMEG-HDI-PPZ-PU).The obtained results are valuable for guiding the improvement and facilitating the localization of fluorinated sulfonic acid resin and extending the application of PTMEG-based polyurethane in biomecial fields.The main work and conclusions were listed as follows:(1)First,Catalyst A as a catalyst(also an initiator),acetic acid(AC)as a co-initiator,and acetic anhydride(ACAN)as a capping agent were employed to induced the ring-opening of THF at 48 oC,370 mmHg,producing PTMEG capped by acetic esters(PTMEA).FTIR and 1H NMR results verified the successful synthesis of PTMEA.The process parameters including the amounts of THF and AC and the reaction time were optimized.The optimal process parameters were: THF/ACAN/AC molar ratios of 3.09 : 0.16 : 0035 and the reaction time of 3.5 h.The produced PTMEA had a Mn of 2065 g/mol.The optimized process was employed for the following evaluation of Catayst B.(2)The appearance and catalytic effects of Catalyst A and B were compared.1)SEM observations indicated that Catalyst A had more compact and uniform surface than Catalyst B.The specific area,measured by using a stereomicroscope,was 0.0021 m2/g for Catalyst A and about twice of the specific area(0.0011 m2/g)for Catalyst B.2)With the increased usage times of the catalysts from 1 to 3,the Mn and yield of PTMEA gradually decreased from 53.63% to 36.78% for Catalyst A while from 42.12% to 18.26% for Catalyst B,indicating that the catalystic effects and reusability of Catalyst B are lower than Catalyst A.The lower specific area of Catalyst B might be responsible.3)After repeatedly using thrice,Ctatalyst A was still transparent with a slight change into yellow,yet Catalyst B turned opaque with more yellowish color,though both became coarser in surfaces.This suggests that Catalyst B has weaker tolerability,which should be attributed to its less compactness and uniformity.(3)PTMEA was transformed into PTMEG by using methanol as alcoholysis agent.FTIR results verified the successful formation of PTMEG.(4)PTMEGs with Mn of ~1000 and ~2000 were employed to produce PTMEG-HDI-PPZ-PU,which are labeled as PU-1 and PU-2,respectively.1)FTIR and 1H NMR results verified the successful synthesis of PTMEG-HDI-PPZ-PU.And the PU-1 has a Mn of 3.4×104 g/mol,however,the PU-2 has a Mn of 13.05×104 g/mol.2)The DSC curves indicated that the glass transition temperatures of both PU-1and PU-2 were close to those of PTMEG,i.e-77 ? ~-80 ?,suggesting excellent low-temperature resistance.In addition,PU-1 had higher melting point yet narrow melting range than PU-2,suggesting better crystallinity and phase separation.This was futher verified by the detected crystalline via XRD,i.e 17.61% for PU-1 and 13.22% for PU-2.The higher content of hard segments in PU-1 should be responsible.