Photoluminescent Properties And Applications Of Maleic Anhydride Alternating Copolymer Derivatives

Aggregation-induced Emission(AIE),as a new type of photoluminescence phenomenon,has been receiving great attention since its first discovery.In recent years,a series of non-conjugated photoluminescent polymers with unsaturated double and single bonds as fluorescent groups have attracted attention.Some of these polymers have,AIE properties,while their emission mechanism is still in dispute.Moreover,most of these non-conjugated polymers can only emit blue-green light,which severely limits their practical application.Therefore,it is of great significance to explore non-conjugated AIE polymers that can emit multiple colors,and to study their emission mechanism and expand their application fields.In this thesis,maleic anhydride alternating copolymers prepared by self-stable precipitation polymerization were used as precursors.By various modification methods,a new series of non-conjugated AIE polymers with multiple colors were prepared,and the structures and optical properties of these polymers were analyzed to investigate their emission mechanism.Subsequently,the polymers were made into various forms to investigate their potential applications in photovoltaic materials,fluorescent fibers,fluorescent antibacterial agents and so forth.The main research contents are summarized as follows.(1)Preparation and application of pH-inducing photoluminescent polylroers with multiple colors.By using poly(maleic anhydride-alt-vinyl acetate)(PMV)and sodium hydroxide as raw materials and adjusting the pH value,a variety of non-conjugated AIE polymers with multiple colors were prepared,and their emission mechanism and potential application were analyzed.The results showed that with the increase of the pH value,the obtained PMV derivative solids could emit cyan,green,yellow,orange and red light,and their maximum emission peaks were located at 507,525,556,595 and 625 nm,respectively with the absolute quantum yield ranged in 12.34?30.93%.Through structural characterization,optical testing and comparative experiments,it was found that pH could affect the interaction of fluorophores such as C=O and C-O groups on the polymer molecular chains in solution,and that pH also induced these groups to form different sizes during the drying process to finally emit different colors.The as-prepared photoluminescent PMV derivatives had excellent heat and ultraviolet resistance,and could be applied in various forms,such as fluorescent powders,films,fibers,hydrogels or the like.In addition,these non-conjugated photoluminescent PMV derivatives could also be used in the preparation of white LEDs.By adjusting the proportion of photoluminescent polymers and the type of LEDs chips,white LEDs with controllable correlated color temperature from cold white(7215 K)to warm white(3486 K)could be fabricated.Pure White LEDs(CIE 1931:(0.33,0.34),correlated color temperature:5606 K,color rendering index:75.1)could be obtained only employing the yellow photoluminescent polymer.Such PMV derivatives greatly enriched the research of non-conjugated AIE polymers,and had low preparation cost and great application prospects.(2)Preparation and application of non-conjugated AIE polymers with dual-emission.Using PMV as precursor,a new family of non-conjugated AIE PMV derivatives with blue/red dual-emission were prepared by one-step method through acid-base neutralization and esterification reaction,and their emission mechanism and potential application were explored.The results showed that the prepared PMV derivatives had blue/red dual-emission performance,among which,blue emission was excitation-dependent,red emission was excitation-independent,and the maximum emission peak of red light could reach 635 nm with the absolute quantum yield of 5.20?6.69%.Further analysis revealed that the dual-emission of the PMV derivatives was due to the formation of two chromophore aggregations in the pendant group during the preparation process,wherein the alkali metal carboxylate group aggregation emitted blue light and the bulky carboxylic ester group emitted red light.The emission intensities of the fluorescent fibers prepared with photoluminescent PMV derivatives and polyvinyl alcohol were found to increase after stretching.And the fibers before and after stretching could emit blue,green and red light under the irradiation of ultraviolet,blue and green light,respectively.Such photoluminescent PMV derivatives with dual-emission had a great promotion effect on the research of non-conjugated AfE polymers,and were expected to be used in the fields of display,anti-counterfeiting and the like.(3)Preparation and application of photoluminescent antibacterial polymers.Firstly,a series of non-conjugated photoluminescent PMV zinc salt derivatives with antibacterial effect were prepared by two-step method using PMV,alkali metal hydroxide and water-soluble zinc salt as raw materials.Then,the modification method was applied to other maleic anhydride copolymers,such as poly(maleic anhydride-alt-a-methyl styrene)crosslinked copolymer(PMASC).The emission,antibacterial mechanisms and potential application in antibacterial plastics were analyzed.The results showed that the obtained non-conjugated PMV zinc salt derivatives had ATE characteristics,and the absolute quantum yield was 10.72?23.90%.Structural analysis revealed that the alkali metal element introduced in the first step could be replaced by zinc ion in the second step,and zinc would crosslink the polymer molecular chains to improve their heat resistance.The photoluminescent PMV zinc salt derivatives had excellent antibacterial activity beyond 99%against Staphylococcus aureus(Gram-negative bacteria)and Escherichia coli(Gram-positive bacteria),and the antibacterial principle was due to the slow release of zinc ion in the polymers.Such PMV zinc salt derivatives could be blended with polypropylene(PP)at 2 wt.‰ addition amount to prepare photoluminescent PP composite with excellent antibacterial properties(antibacterial rate>99%).The prepared photoluminescent PMASC zinc salt derivative had excellent thermal stability with the maximum weight loss temperature up to 393? and antibacterial property(antibacterial rate>99%).This PMASC derivative could be used to prepare photoluminescent antibacterial PP materials.When the addition amount was only 2 wt.‰,the antibacterial rate of the obtained PP composite before and after boiled at 50? for 16 hours was greater than 99%,showing high efficiency and long-lasting antibacterial properties.The photoluminescent antibacterial polymers prepared by this modification method had the advantages of low cost,good heat resistance,high efficiency and long-lasting antibacterial effect,and were expected to be widely used for research and development of various antibacterial products.