Functionalization And Application Of Visible-light-degradable Picolinium-contained Polymers Via The Mediated Electron Transfer

Photodegradable polymers can present specific degradation behaviors under light irradiation,leading to significant changes in their structures and properties.These properties enable their promising applications in drug delivery,bio-sensing and stretchable electronics.However,most photodegradable polymers are based on nitrobenzene and p-hydroxybenzoyl-contained polymers,which are photodegraded by high-energy UV light,limiting their applications,especially in the biological field.Therefore,it is of great significance to develop a simple,biocompatible polymeric system to address this challenge.Recently,the visible-lighttriggered mediated-electron-transfer process has been widely used to remove the protecting groups of NAP(N-alkyl-4-picolinium)from molecules with the catalysis of tris(bipyridyl)ruthenium(II).This biocompatible approach can be achieved at very mild conditions.Following this inspiration,in this thesis,we design two NAP-contained groups for synthesizing visible-light-photolabile polymers,and further explore their applications in light-responsive surfaces and hydrogels.The main content is divided into the following two parts:(1)An asymmetric pyridinium ester polymer that can be rapidly degraded under visible / near-infrared emission is designed and synthesized.Here,we design an asymmetric picolinium-containing photodegradable polymer(P1)and other two picolinium-containing photodegradable polymers(P2-3)to fabricate visible-light/NIR-degradable multilayer films.The effects of polymer molecular structures on the degradation behavior of Lb L films are investigated.The results indicate that introducing the asymmetric picolinium group into the photolabile P1 can significantly enhance the degradation rate of Lb L films compared with P2 and P3.Also,the fast degradation of this film can be realized upon NIR irradiation with the assistance of upconversion nanoparticles,thus reinforcing its great potential in the materials science and biological fields.As a proof-of-concept,a selective degradable film is demonstrated by sequentially exposing to specific lights.Moreover,P1 and its degradation product are low-toxic,and the as-prepared biocompatible Lb L film benefits to cell proliferation.All results in this work reveal that such a novel visible-light/NIR photolabile polymer and the fast degradable Lb L film can inspire further applications in multi-responsive systems with other stimuli.(2)A multi-responsive photodegradable picolinium-containing gelator was designed and prepared.The gelator can be fast synthesized through esterification and alkylation reactions.Picolinium-containing photolabile groups enable the gelator to be rapidly degraded using tris(bipyridyl)ruthenium(II)and ascorbic acid.Dynamic boronic bonds and disulfide bonds make the gelator response to various small molecules such as DTT,GSH,which has a very promising application in cancer therapy.The PVA-based gel make the gelator as a building block for the preparation of multi-responsive degradable gel.