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Design and Characterization of Dynamic Polymers with Smart Properties Based on Acylhydrazone Bond

Author: JiangYi
Tutor: YanDeYue；ZhuXinYuan
School: Shanghai Jiaotong University
Course: Polymer Chemistry and Physics
Keywords: constitutional dynamic chemistry reversible covalent bond dynamic polymer (dynamer) acylhydrazone bond self-assembly pH response tunable release α-cyclodextrin polyrotaxane reversible chain exchange temperature response
CLC: O631
Type: Master's thesis
Year: 2009
Downloads: 54
Quote: 1
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Abstract


Supramolecular chemistry and dynamic covalent chemistry are two of the hot research topics in chemistry in recent years, which belong to constitutional dynamic chemistry in the view of their dynamic properties essentially. Dynamic bonds, including supramolecular bonds and reversible covalent bonds, are the key concept in constitutional dynamic chemistry. Thus, the polymers constructed by dynamic bonds are named as dynamic polymers, which are also called as dynamers for short. Such dynamic polymers are endowed with smart properties for the dynamic nature of the reversible bonds which can be tunable formed and broken in mild conditions.Acylhydrazone bond, an important kind of reversible covalent bond, is being widely investigated in dynamic covalent chemistry, which has smart properties under the control of pH change and temperature catalyzing. In the present work, based on the dynamic nature of reversible acylhydrazone bond, several different kinds of dynamic polymers with smart properties have been successfully constructed. The thesis is mainly consisted of two parts as follows:(1) Acylhydarzone bond is employed to construct amphiphilic dynamic di-block copolymers with smart properties. Through atom transfer radical polymerizations and polymer end-modifications, amphiphilic dynamic block copolymer systems, which are polystyrene-b-poly (ethylene glycol) (PS-b-PEG) with acylhydrazone bond, are formed via condensation of acylhydrazine bonds with aldehyde bonds. Similar with conventional amphiphilic block copolymers, the amphiphilic dynamic block copolymer systems (PS-b-PEG) can be self-assembled into diverse morphologies in dilute selective solvent. Based on the pH responsive property of acylhydarzone bond, such self-assembled amphiphilic dynamic block copolymer systems can undergo reversible transformation between self-assembly and disaggregation under the catalysis of pH change in solution. More importantly, these self-assembled dynamic block copolymer systems can be used as smart system in dye/drug encapsulation, which have tunable release property under the control of pH change in solution.(2) Utilizing the temperature responsive property of acylhydrazone bond, a new route to construct polyrotaxane is developed via reversible chain exchange between acylhydrazone bonds. Dumbbell-like poly (ethylene glycol) (PEG) derivatives with acylhydrazone bonds are implemented to constructα-cyclodextrin-based polyrotaxane at high temperature, which could be considered as a new route to prepare polyrotaxane. Unlike the general methods to prepare polyrotaxane, which need the prerequisite approaches to prepare pseudorotaxane or polypseudorotaxane, this novel method developed doesn’t need such steps. By simply mixingα-cyclodextrins (α-CDs) with dumbbell-like PEG derivatives with reversible covalent bonds at 120 oC, the PEG crystals melt. Meanwhile, the reversible chain exchanges between acylhydrazone bonds occur, which provide the chance forα-CDs slipping into the PEG chains. During such reversible exchange processes, more and moreα-CDs are threaded onto the PEG chain, which leads to the formation of polyrotaxane ultimately. This novel method has been proven by analyses of diffusion-ordered NMR, WAXD, 1H NMR, solid-state 13C CP/MAS NMR, DSC and UV-Vis together.

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CLC: > Mathematical sciences and chemical > Chemistry > Polymer chemistry ( polymer ) > Polymer physics and physical chemistry of polymers
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