No abstract

Three water-soluble quaternized cellulose derivatives (QCs) with degree of substitution (DS) values of 0.38, 0.50, and 0.74 were synthesized in NaOH/urea aqueous solutions. The flocculation characteristics of QCs have been evaluated in montmorillonite (MMT) suspensions and simulated dye (Reactive Red) aqueous solutions by spectrophotometry. The results showed that QCs were effective flocculating agents for MMT over a wide range of pH values, and the flocculation efficiency of MMT was up to nearly 100%. Decolorization efficiency of Reactive Red dye reached 93% under optimum conditions. In vitro antimicrobial activity of QC was evaluated by determining minimum inhibition concentration (MIC) values against Gram-positive bacteria (S. aureus) and Gram-negative bacteria (E. coli), respectively. The results showed that QC could strongly inhibit the growth of E. coli and S. aureus. Therefore, quaternized cellulose is applicable as a novel wastewater treatment agent with high flocculation efficiency as well as effective antimicrobial activity.

A method was developed to synthesize molecular brushes with polymethacrylate backbone and ultrahigh density of grafted side chains (SCs), i.e., 1.34 SCs per backbone carbon atom, using accelerated copper-catalyzed azide–alkyne cycloaddition (CuAAC) grafting-onto strategy. This acceleration effect that benefits from the complexation of triazole with Cu was first confirmed in two model CuAAC reactions of (a) 1:1 molar ratio of a diazide compound and an alkynyl-terminated poly­(ethylene oxide) (ay-PEO18 with average degree of polymerization DP = 18) and (b) 1:1 molar ratio of a dialkyne compound and an azido-terminated N3-PEO18. It was found that both model reactions produced ditriazoles as major products, although the former reaction exhibited a higher yield of PEO–PEO dimers, demonstrating better CuAAC acceleration effect. Following this principle, polymethacrylate backbones with multiazido dangling groups were subsequently used for grafting-onto reaction with ay-SCs to prepare an array of molecular brushes with high grafting densities. Within our investigation, all these CuAAC grafting reactions finished within 10 min and introduced different SCs, including PEO18, PEO113, poly­(methyl acrylate) (PMA31), and polydimethyl­acrylamide (PDMA46). The grafting density was affected by the composition of SCs and the initial molar ratios of ay-SCs to azido groups. When applying linear SCs with thinner structure, such as ay-PEO113, the highest grafting density was obtained (1.34 SCs per backbone carbon atom) on both longer polymethacrylate backbone (DP = 430) and shorter backbone (DP = 180).

Allyl cellulose can be synthesized from cellulose and allyl chloride in NaOH/urea aqueous solutions and is further used to synthesize a variety of new cellulose derivatives through the thiol–ene click reaction.

A hyperbranched polymer with multilayer structure was developed to demonstrate the possibility of highly efficient tandem functionalization reactions at different domains within one nanostructured platform. The polymer scaffold was constructed by chain-growth copper-catalyzed azide-alkyne cycloaddition polymerization of three functional monomers with sequential monomer addition in one pot. Subsequent reactions with different monomer units resulted in efficient functionalization of each segment with construction of a highly sophisticated polymer structure by a robust procedure. As a proof of concept, the ability of this polymer structure to quantitatively load six species of guest molecules through three different types of conjugation reactions was demonstrated.

The first synthesis of acid-degradable hyperbranched polymers using chain-growth CuAAC click polymerization of an AB3 monomer.

A series of AB 2 -R monomers that were composed of one alkynyl group (A), two azido groups (B 2 ), and a dangling group (R) were applied in the copper-catalyzed azide−alkyne cycloaddition (CuAAC) polymerization for synthesis of hyperbranched polymers. Several structural variables, including the linker between the alkynyl group and the diazido unit (S1), the linker between the two azido groups (S2), and the composition of R group, were systematically changed to study their effects on the polymerization kinetics, the molecular weights, and the degree of branching (DB) of the hyperbranched polymers. Within the investigation, all polymerizations eventually showed chain-growth features although their starting moments when exhibiting linear increase of molecular weights based on conversions were delayed by the increased length of S1 linker, but little influenced by S2 and R groups. The AB 2 -R monomer with longer S1 linker, due to slower hopping of Cu catalysts between neighboring structural units, resulted in more leftover oligomers and decreased overall molecular weights. High DB > 0.75 was achieved in all hyperbranched polymers with various S1 lengths and R groups and slightly influenced by the steric hindrance and the rate of catalyst hopping. Instead, the increase of S2 linker from C2 to C4 lowered the reactivity of the second azido group in linear units and resulted in an evident decrease of the DB from DB = 0.73 to 0.55, respectively.

A one-pot method was developed for in situ preparation of linear–dendritic copolymer assemblies via click polymerization-induced self-assembly (CPISA).