Zi-Long Li

One-pot synthesis of polyamides with various functional side groups via Passerini reaction

Polyamides with various functional side groups were synthesized via Passerini reaction in a one-pot approach. The polymerization conditions and kinetics as well as the resulting polymer structures were thoroughly investigated. The facile introduction of various pendant groups, especially alkynyl and alkenyl groups, provides a platform for efficient post-polymerization modification by click chemistry.

Facile synthesis of multi-block copolymers containing poly(ester–amide) segments with an ordered side group sequence

We report a facile method for the synthesis of multi-block copolymers consisting of poly(ethylene glycol) (PEG) and poly(ester–amide) segments with an ordered side group sequence via multicomponent polymerization based on the Passerini reaction (PR). The technique involves the polymer supported liquid-phase synthesis of three PEG diacid macromonomers (M1–M3) via stepwise PR with tert-butyl isocyanoacetate and a functional aldehyde followed by selective hydrolysis, and the final multicomponent polymerization of M1–M3 with phenylacetaldehyde and 1,6-diisocyanohexane.

Acyclic diene metathesis polymerization of tailor-made monomers towards sequence-regulated vinyl copolymers

Acyclic diene metathesis polymerization (ADMET) enables convenient transfer of sequential information of the designed monomers to the corresponding sequence-regulated copolymers. In this study, two structurally symmetric monomers, M1 and M2, were synthesized via atom transfer radical addition (ATRA) of diethyl meso-2,5-dibromohexanedioate with 1,5-hexadiene and 1,7-octadiene, respectively. Thus, sequenced segment of VB-EA-EA-VB (VB and EA represent vinyl bromide and ethyl acrylate, respectively) was incorporated into the ADMET diene monomers. ADMET polymerization of these two monomers with Grubbs first generation catalyst (Grubbs-I) was performed in CH2Cl2 at 40°C for 5 days under nitrogen purge. Effects of catalyst amount, monomer concentration and methanol precipitation on the Mp and PDI of polymers were investigated by GPC, and the structures of the formed polymers were characterized by NMR. Our results indicate that using 3.0 mol% of Grubbs-I to monomer can afford polymers with high Mp. Moreover, selective precipitation in methanol enables complete removal of low molecular weight components from the crude products. Meanwhile, M2 exhibits higher ADMET polymerization reactivity than M1 due to its capability of suppressing negative neighboring group effect.

Synthesis of linear functionalized polyesters by controlled atom transfer radical polyaddition reactions

We report on the facile synthesis of a range of new linear functionalized polyesters by controlled atom transfer radical polyaddition reactions. One bis-styrenic type monomer, 1,2-bis(4-vinylbenzyloxy)ethane (AA), and two bis-methacrylate type ATRP initiators, 1,2-bis(2-bromoisobutyryloxy)ethane (BB) and bis[2-(2-bromoisobutyryloxy)ethyl]disulfide (BssB), were synthesized. The polymerizations of monomer AA with BB and BssB were carried out in anisole at 0 °C, using Cu/CuBr2 coupled with N,N-bis(2-pyridylmethyl)octylamine (BPMOA) as the catalyst. The polymerization kinetics were investigated and the polymers were characterized by GPC and NMR, both confirming the step-wise mechanism with the formation of the expected linear polyesters having pendent bromides. When BssB was used, additional disulfide groups were incorporated in the polyester main chain, imparting a tunable degradation mechanism to the polyester. Moreover, the pendent bromides on the polymers could serve as initiation sites or precursors to azides to prepare biodegradable graft copolymers. This has been proven by two examples, reactivating the pendent bromides at room temperature to initiate the ATRP of other methacrylates, and transforming these groups into azido-groups by substitution reaction followed by click chemistry with alkynyl-terminated polyethylene glycol.