Design And Synthesis Of Bio-Based Polyester/Polyamide Elastomers Using Molecular Chain Odd-Even Effect

Both polyester and polyamide are relatively common synthetic polymer materials at present.However,due to high molecular chain regularity or strong interchain hydrogen bonding,the existing commercial polyesters and polyamides are both plastics.Considering that ester groups and amide groups can impart biocompatibility and biodegradability to elastic polymer materials,it is of great significance to design and develop polyester and polyamide elastomer materials.In addition,thanks to the prosperity and development of the bio-based polyester and polyamide monomer industry in recent years,the construction of bio-based polyester and polyamide elastomer materials that meet the requirements of the national dual-carbon strategy has also become a current research focus.Relevant studies have shown that multi-component copolymerization of five or more components is an important way to construct amorphous polyester or polyamide elastomer materials,and then the use of too many components will increase the difficulty of industrialization and overall cost of products,so it is important to build polyester or polyamide elastomers for low-component systems.Combined with the"odd-even effect"(that is,the crystallinity of polymers with odd-numbered carbon chain structural units is significantly weaker than that of polymers with even-numbered carbon chain structural units with similar structure),it can be seen that reasonable regulation of the composition and content of odd-numbered carbon chain structural units is expected to achieve low-component polyester or polyamide elastomers.In this paper,the effects of different odd-even carbon chain monomers on the properties of bio-based polyester and polyamide were comparatively studied,and new bio-based polyester and polyamide elastomers were designed and synthesized using the principle of"odd-even effect".The main work is as follows:The first part of this thesis(Chapter 2),we prepared three series of quaternary copolyesters:poly(butanediol/pentanediol/adipic acid/itaconic acid)copolyester(PBPe AI),poly(pentanediol/succinic acid/adipic acid/itaconic acid)copolyester(PPe SAI),poly(pentanediol/succinic acid/glutaric acid/itaconic acid)copolyester(PPe SGI),which segments with different odd-even properties,from polymerizing of biomass diacids and diols(a small amount of itaconic acid is introduced to provide chemical cross-linking points),and the effects of even-even,odd-even and odd-odd structures in the molecular chain on the crystalline properties of polyesters were studied.In the follow-up work,through Differential Scanning Calorimetry(DSC)and Wide-Angle X-ray Diffraction(WAXD),it was found that the ability of different odd-even chain structures to destroy the crystallinity of the polymer is odd-odd structure>odd-even structure>even-even structure.PBPe AI copolyesters,which with even-even and odd-even segment structures are in crystalline plastic state at low temperature;PPe SGI copolyesters,which only with odd-even segment structures can obtain elastomers with amorphous structures when the adipic acid content is less than70 mol%,PPe SGI copolyesters which with odd-even and odd-odd segment structures show as an amorphous elastomer under any monomer ratio.Then,the PPe SAI copolyesters were selected for subsequent composite nano-silica,and an elastomer composite material with tensile strength greater than 12 MPa and elongation at break greater than 300%,which can meet some engineering applications.In the second part of this thesis(Chapter 3),we synthesized a series of binary polyamides by melt polycondensation,which segments with different odd-even properties,from Hydrogenated Fatty Dimer Acid(HFDA)andα,ω-diamine with nine different carbon chain lengths from C2 to C10,the relationship between the"odd-even effect"on hydrogen bonding and crystalline properties in HFDA-based polyamide materials was studied.Then by combining FT-IR,DSC,and WAXD analysis,it is found that the hydrogen bonding of even series polyamide is significantly stronger than that of odd series polyamide,and the even series polyamide sample has two crystal forms ofαandγafter sufficient annealing,while the odd series polyamide only showedγcrystal form.In the third part of this thesis(Chapter 4),HFDA and bio-based 1,5-pentanediamine(Pe DA)and 1,10-decanediamine(De DA)were selected to synthesize ternary copolyimide(PPe De HA),and the regularity of the polyamide molecular chain is destroyed by means of terpolymerization.When the De DA content is 60 mol%and above,PPe De HA is similar to the above even-numbered series of binary polyamides,exhibiting two crystal forms ofαandγ,while the Pe DA component is in the majority(50mol%and above),PPe De HA only exhibits theγcrystal form.PPe De HA did not yield during the tensile test when the De DA content was 20-60 mol%,which was in line with the characteristics of elastomeric materials and belonged to elastomeric materials.However,due to the strong rigidity of the molecular chain,the T_g(-5～0℃)of the synthesized polyamide elastomer is high,which cannot meet its application in the field of elastomers.In addition,in order to improve the flexibility of the molecular chain bio-based polyether diamine(PEA),which has a long flexible main chain to copolymerize with HFDA and Pe DA to obtain a ternary copolyamide(PPe PEHA),which with low T_g(-65～-10℃).Due to the existence of the long-chain amorphous PEA and the odd-numbered structure of Pe DA,the PPe PEHA copolyamide behaves as an amorphous elastomer,and it is expected to obtain a polyamide elastomer with application value.