Synthesis And Properties Of Polyarylates Based On Phenolphthalein

Polyarylates have attracted much attention in the field of high-performance polymer materials due to their excellent heat resistance and mechanical properties,which have been widely used in automobile manufacturing,aerospace,electronic equipment and other high-tech fields.With the development of new technologies,polymer materials with excellent comprehensive properties and diversified functions have become the focus of scientific research.And the design and synthesis of polyarylate with excellent heat resistance and high mechanical strength,as well as good solubility and functional properties,is of great significance for giving full play to the inherent advantages of polyarylates and broadening their application fields.In this paper,through molecular design,a twist and non-coplanar phenolphthalein with bulky pendent group was successfully introduced into the polyarylate main chain via low temperature solution polymerization/interfacial polymerization.On this basis,a series of high-performance polyarylates were prepared by adjusting the aggregation structure,electron donor receptor action,and the introduction of fluorine-containing structures.And the effects of different structures on aggregation,mechanical properties,thermodynamics and dielectric properties were investigated.The research is composed of four parts.1.Phenolphthalein-based polyarylate homopolymers of different structures were synthesized by low temperature solution polymerization.The phenolphthalein-based polyarylate containing para-benzoyl structure（CPAR）exhibited good heat resisitance,and the glass transition temperature（T_g）was 325℃,which was 52℃higher than that of phenolphthalein-based polyarylate containing isophthaloyl structure（CPAR-I）.A series of CPARs with different molecular weight（M_n～1.23×10⁴-7.24×10⁴ g/mol）were prepared by optimizing the synthesis conditions.And the increase of molecular weight contributes to the further improvement of heat resistance and mechanical strength,but it also leads to a significant increase in melt viscosity.CPAR is an amorphous resin with excellent solubility,which could be dissolved in dichloromethane,1-methyl-2-pyrrolidinone（NMP）,N,N-dimethylformamide（DMF）and other polar aprotic solvents at room temperature.In addition,the CPAR coating films has good comprehensive performance.2.The crystalline chain segment was introduced into the molecular main chain of CPAR through copolymerization,and the aggregation structure of polyarylate was adjusted by controlling the ratio of crystalline chain segment to amorphous chain segment in the polymer molecular chain,and the effects of structure composition on thermal properties,mechanical properties,solubility and high-temperature rheological behavior were studied.First,the structure of bisphenol A was successfully introduced into the main chain of CPAR by one-step interfacial polymerization,and a series of random copolyarylates（ACPARs）of different compositions were obtained.The resulting copolyarylates had good thermal properties,with T_g 191-314℃,and T_5%in nitrogen 441-475℃.With the increase of bisphenol A content in ACPARs,the elongation at break of films increased gradually.When the bisphenol A content of ACPAR was 70%（ACPAR70）,the tensile strength reached the highest,the aggregation state changed from amorphous to semi-crystalline,and the melt viscosity decreased significantly.ACPAR70 has good comprehensive performance.Secondly,a series of block copolyarylates（Blocks）of different sequence lengths were prepared by step interfacial polymerization.Compared with the random copolymer（ACPAR50）of the same composition,the Block 1 showed a semi-crystalline aggregation state,and its melt viscosity decreased.Block copolymers have good thermal and mechanical properties.With the increase of the sequence length of phenolphthalein chain,the aggregation state changed from semi-crystalline to amorphous state,and the T_g,melt viscosity and bending modulus gradually increased.3.In order to improve the thermal and mechanical properties of polyarylates,we have designed and synthesized the copolyarylates（FCPARs）with the electron donor ability of fluorene group.All the FCPARs had a high T_g（277-306℃）,with T_5%in nitrogen 461-510℃and residual carbon rate 48-60%at 700℃,indicating that FCPARs have good thermal properties.FCPARs exhibited good solubility and film-forming property,and the flexible films could be prepared via solution processing,which possessed good mechanical properties.When the bisphenol fluorene content of FCPAR was 30-50%,it showed the best mechanical properties.4.Considering that 2,3,5,6-tetrafluorophenylene structure could endue the polymer with good thermal stability,hydrophobicity and low dielectric constant,we introduced 2,3,5,6-tetrafluorophenylene structure into the phenolphthalein-based polyarylate molecular chain,and successfully prepared the semi-fluorinated phenolphthalein-based polyarylate（CPAR-F）containing 2,3,5,6-tetrafluorophenylene by low temperature solution polymerization.CPAR-F had a high T_g（300℃）,the T_5% in nitrogen atmosphere reached 472℃,and the carbon residue rate at 700℃ increased to 60%,indicating that CPAR-F has good thermal stability.Meanwhile,CPAR-F showed better solubility than CPAR,and the film prepared by solution processing had good mechanical properties.Compared with CPAR,the water absorption rate and dielectric constant of CPAR-F were significantly reduced,indicating that the introduction of 2,3,5,6-tetrafluorophenylene structure improves the hydrophobicity and effectively reduces the dielectric constant.