A series of diblock copolymers MePEG-b-PBYP were firstly synthesized by the ring-opening polymerization of 2-(but-3-yn-1-yloxy)-2-oxo-1

3

2-dioxaphospholane (BYP) using polyethylene glycol monomethyl ether (MePEG) as the macroinitiator and Sn(Oct)2 as catalyst.Subsequently

the alkyne groups on PBYP blocks were modified with three mercaptans by thiol-yne click reaction to yield polyphosphoester-based diblock copolymer with various pendant functional groups (NH2

COOH and SO3Na).The molecular structures

molecular weights

and molecular weight distributions of the block copolymers were characterized by NMR and GPC analyses.MTT assay indicated that these block copolymers show relatively low cytotoxicity against L929 fibroblast cells.The microgels were prepared through electrostatic interaction between these oppositely-charged polyelectrolytes.The particle size

zeta potential and morphologies of the particles were also analyzed by DLS and TEM techniques.In order to enhance the physical crosslinking

-cyclodextrin (-CD) was added into the system to interact with PEG chain via inclusion complexation

resulting in the formation of stronger crosslinked hydrogels.SEM was utilized to observe the surface morphologies of microgels and hydrogels

XRD was used to analyze the inclusion complexation and rheology test was employed to monitor the gelation kinetics of the hydrogels.These biodegradable hydrogels with good biocompatibility and favorable mechanical properties provide a promising injectable material and have potential applications in the fields of controlled drug delivery and tissue engineering.