Synthesis And Biodegradability Study Of Novel Polyamide-imides Based On The Amino Acids

Nowadays,polymer materials play an increasingly important role in people's lives.They have changed our life greatly.While polymer materials bring convenience to us,their difficult degradability brought multiple potential hazards on ecological security and human survival,so it has been a hot trend to develop green materials and biomaterials,especially degradable materials.Polyamides(PA)and polyimides(PI)are a group of materials that projects good function,such as splendid heat resistance,insulating properties and chemical resistance.However,its low dissolubility and rigid properties limit its further application.Polyamide-imides(PAIs)based on amino acids is one kind of significant material,which combine the thermal resistance associated with PA,and the easy processing associated with PI.For PAIs,the introduction of amino acids can not only improve its degradability,but its biocompatibility,bio-absorbability and adequate mechanical properties,and the reports on this aspect are very rich.This work mainly divided into three parts.The first part is the preparation and characterization of diacid monomers based on amino acids.The diacid monomers were obtained by the reactions of seven different types of amino acids(L-alanine,D-alanine,L-phenylalanine,D-phenylalanine,L-2 aminobutyric acid,L-positive valine,L-tryptophane)and pyromellitic dianhydride.The diacid monomers were characterized by IR and 1H-NMR spectra,elemental analysis,and specific rotation test.Through the comparison of different diacid monomers' optical rotation data,it is easy to find that the specific rotation has hardly changed,but the specific rotation of 2d and 2e is 100°-200° higher than 2a-2c.It means that the presence of rigid group such like aromatic ring benzimidazole ring makes the diacid monomers' specific rotation increase.Besides,for the diacid monomers that have the same structure but different chiral,there are not too different between the absolute value of specific rotation,but the optical rotation are inverted.This proofs that the racemization didn't happened during the synthic of diacid monomers.The second part is the preparation and characterization of PAIs derived from amino acids.The PAIs were obtained by the reactions of diacid monomers and 4,4'-diaminodiphenyl ether through the imine dicarboxylic acid method.The structure and purity of PAIs were characterized by IR and 1H-NMR spectra,elemental analysis,and specific rotation test.Thermal properties of these materials were evaluated by the gravimetric analysis(TGA)and differential scanning calorimetry(DSC).Through the comparison between diacid monomers and polymers,it found that the optical rotation of diacid monomers is higher than the PAIs.It means that the physical superposition of optical rotation did not happened during the condensation reaction,but the PAIs' optical rotation decreased compared to the diacid monomers.This reflects the importance of the conformational of polymer chains.The third part is the impact of amino acids' structure and chiral on the thermal and degradability properties of PAIs.Fist off,the amino acids' structure and chiral effect on PAIs' thermal properties were observed through a series of thermal tests.It turned out that the major factor for the thermal performance of PAIs will be the structure of polymer's main chain,and the internal plasticization effect and volume effect work together to the Tg values of PAIs.The PAIs that with L-bonds has better thermal performance than that with D-bonds,and the PAIs that with L-D bonds or D-L bonds have good thermal properties than that with L-L bonds or D-D bonds.The variability of degradation of these polymers were investigated through soil degradation assay.And the variations of water contact angles,molecular weights,structures and appearances during degradation period were characterized by a series of characterization methods.The results shows that when the side groups of amino acids which are introduced into PAIs are n-alkanes chain or rigid groups,the increase of alkane chain or rigid groups' volum could decrease the biodegradability of PAIs.Besides,microorganism prefers degraded the PAIs that with L-bonds,and the PAIds that with L-L bonds have better degradability performance than that with L-D bonds or D-L bonds,and the PAIs that with L-D bonds or D-L bonds have better biodegradability performance than that with D-D bonds.