Preparation And Properties Of Functional Polyacetylene

As an important class of functional polymer matericals,design and synthesis of functional polyacetylenes has attracted considerable interest.Incoporation of functional pendants into the polymer backbone confers polyacetylene intriguing funtions such as nonlinear opticle properties,liquid crystallinity,fluorescence,biological activity,and gas permeability.This make functional polyacetylenes appealing in potential applicatios in the fields of chiral separation,liquid crystal materials,fluorescence materials,gas separation,etc.In this thesis,we explored postpolymerization modification protocols for the synthesis of functional polyacetylene,and the properties of the obtained polymers were investigated.The details are listed as follows1.A postpolymerization modification approach based on dynamic imine chemistry for the facile synthesis of a variety of functional polyacetylenes from a polymeric substrate was developed.A high molecular weight polyacetylene bearing imine moieties(P?-1)was synthesized and used as the parent polymer.Postpolymerization modification of P?-1 with a series of amines through transimination afforded the target products(?-1 a-P?-le).Transimination reactions proceeded smoothly under mild conditions without any catalysts,and complete substitution was confirmed under suitable conditions by 1H NMR spectroscopy.Incorporation of chiral pendant groups induced predominantly one-handed helicity along the polyene backbone(P?-1a-P?-1d).P?-1e formed from 4-amino-2,2,6,6-tetramethylpiperidine-l-oxyl exhibited reversible charge/discharge ability,indicative of its capacity as an electrode-active material for organic-based battery.Given the commercial availability of diverse amines and mild reaction conditions,transimination reaction is considered as a versatile polymer modification tool for the preparation of functional materials2.Postpolymerization modification based on selective amide transformation for preparation of functional polymers is relatively underexplored,although amide as an important building motif is ubiquitous in biological and synthetic polymers.Inspired by recent advances in amide chemistry,N,N-Boc2-benzamide group-containing polyacetylene(P?-1)was synthesized which used as a polymer substrate for post-modification.Transamidation of PIII-1 employing amine nucleophiles,(R)-and(S)-1-phenylethanamine and anthracen-9-ylmethanamine,proceeded completely under mild conditions to produce polymers with predominantly one-handed helical structures and enhanced luminescence(P?-1a-P?-1c).Modification with alcohols needed more forcing conditions to achieve full substitution.Incorporation of 2-(2-(2-methoxyethoxy)ethoxy)ethanol resulted in a dramatical increase in surface energy of P?-1d.PIII-le from 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl exhibited reversible charge/discharge ability as a cathode material.3.Given the diverse structural availability and several reactions involving amines,two postpolymerization modification approaches were utilized for the facile synthesis of functional polyacetylenes through the rational design of the structure of polymerization precursor.Aryl carbamate-containing polyacetylene(PIV-1)was synthesized and used as a polymer substrate for post-modification.Modification of P?-1 with amines through nucleophilic substitution afforded the target polymers with pendent urea-groups(P?-1 a and P?-1b).Addition of anions into the P?-1b/THF solution resulted in distinct color changes which depended on the type of onions.Meanwhile,red-shift of the absorption peak in the UV-vis spectrum was observed,suggesting the formation of hydrogen bonds between the urea group and anions.These results indicate that P?-1b can be used as an effective anion recognition material.On the other hand,a thiolactone functionalized polyacetylene(P?-2)was synthesized,and employing it as polymer presusor,a series of functionalized polyacetylenes were synthesized by the amine-thiol-ene conjugation This modification approach offers a route to produce polymers bearing two functionalities in each repeat unit4.Two thianthrene-containing acetylenic monomers were designed and synthesized and polymerized with[(nbd)RhCl]2/Et3N catalyst to give polymers PV-1 and PV-2 with high molecular weight(Mn=33 ×103 and 44 × 103).Thermogravimetric analysis revealed that the onset temperature weight loss of the polymers were over 240?,indicating relatively high thermal stability.Both polymers displayed reversible redox reactions in composite electrodes.The PV-1 and PV-2-based cathodes showed initial specific capacities of 33 and 100 mA h/g,respectively,at a high charge/discharge potential of 4.1 V vs Li/Li+.While the capacity fading in both systems occurred during cycling test,the specific energy capacity of PV-2-based battery remained over 240 mW h/g after 20 test cycles,which is higher than those of the conventional Li-ion batteries(?200 mW h/g).