Synthesis Of Hydroxyl Functionalized Polyethylene Oxides

Polyethylene oxide（PEO）is widely used in applications such as detergents,cosmetics,paper coatings,polyurethane,textile modification,construction chemistry,and biomedical applications due to its excellent water solubility,biocompatibility,and non-toxicity.However,PEO,as a linear polyether,contains only one or two hydroxyl groups at the chain end,lead to a great limitation in the functionality of the PEO materials.Increasing the number of hydroxyl groups in PEO to prepare PEO functionalized with hydroxyl groups in the chain has been the focus of PEO synthesis.In this paper,The homopolymerization of two functionalized monomers,isopropylidene glycidyl glycidyl ether（IGG）and（R）-glycidyl butyrate（RGB）,and their copolymerization with ethylene oxide（EO）catalyzed by i-Bu₃Al/H₃PO₄/DBU has been carried out.The hydrolysis of the obtained homopolymers and copolymers afforded the corresponding hydroxyl functionalized PEO with different structures and high molecular weight.The distribution and content of hydroxyl groups could be precisely regulated in these hydroxyl functionalized PEO.1)The ring-opening polymerization of IGG by i-Bu₃Al/H₃PO₄/DBU afforded IGG homopolymer in a high activity.The hydrolysis of ketal structures in the IGG homopolymer gave hydroxylated product with high molecular weight（M_n=9.2×10⁴）simply and efficiently.The copolymerization of IGG and EO by i-Bu₃Al/H₃PO₄/DBU has also been successfully achieved to afford the EO-IGG copolymers with controllable compositions in 100%yield by changing the feed ratio of IGG and EO.The hydroxyl functionalized PEO with high molecular weight were obtained in 100%yield after hydrolysis of ketal structures in the EO-IGG copolymers.The hydroxyl groups with controllable content were randomly distributed in the PEO.The molecular weight of hydroxyl functionalized PEO（M_n=6.5×10⁴～18.1×10⁴）can be regulated by changing the ratio of monomers to catalyst.By the two-step reaction of copolymerization and hydrolysis,the hydroxyl functionalized PEO with high molecular weight were obtained in 100%yield,and the two adjacent hydroxyl groups with controllable content were randomly distributed in the polyethylene oxide.2)The ring-opening polymerization RGB by i-Bu₃Al/H₃PO₄/DBU afforded RGB homopolymers with high stereoregularity.The hydrolysis of carboxylic ester structures in the RGB homopolymers gave hydroxylated product with high stereoregularity and controlled molecular weight（M_n=0.4×10⁴～3.5×10⁴）by changing the ratio of RGB to catalyst.The sequential and simultaneous copolymerization of RGB and EO by i-Bu₃Al/H₃PO₄/DBU has also been successfully achieved to afford the EO-RGB copolymers with controllable compositions in 100%yield by changing the feed ratio of RGB and EO.The hydroxyl functionalized PEO with high stereoregularity and high molecular weight（M_n=18.3×10⁴）were obtained in 100%yield after hydrolysis of carboxylic ester structures in the RGB-IGG copolymers.The hydroxyl groups with high stereoregularity and controllable content were blocky distributed in the PEO.The RGB-IGG block copolymers with different block structure were conveniently obtained by sequential copolymerization of RGB with EO.The RGB-IGG statistical copolymers with gradient structure,controllable compositions and molecular weight were conveniently obtained by simultaneous copolymerization of RGB with EO.The hydroxyl groups with high stereoregularity could be blockly and gradiently incorporated into PEO quantitatively.