Synthesis of a Novel Polycarboxylate Superplasticizer with Hyperbranched Structure

Abstract

It is well established that the performance of super-plasticizer (PCE) is mostly determined by its molecular structure. This research tends to combine PCE with hyperbranched polymer and design PCE molecule structure, aiming to enhance the water-reducing performance of PCE. Here, a novel PCE with hyperbranched molecular structure (HBPCE) was synthesized through two steps. With diallylamine, methyl propenoate and trihydroxymethylpropane as raw material, firstly, a hyperbranched monomer B was successfully synthesized. Then through free radical polymerization of methylallylpoly oxygenethene ether 2400 (HPEG 2400), propenoic acid (AA) and the monomer B in aqueous solution, the final product HBPCE was obtained. 1 H nuclear magnetic resonance (1H NMR) and infrared spectroscopy (IR) measurements were used for structural characterization, and gel chromatography was used to measure the molecular weight distribution of HBPCE. In addition, performances of HBPCE in cement paste were investigated. It is concluded that HBPCE has a good dispersing effect on cement paste and the water reduction ratio is up to 38.6%.Since came out in the 1980s, polycarboxylate superplasticizers (PCE) have been increasingly used in cement and concrete industry, such as buildings, bridges and dams fields. [1][2][3] Traditional PCE polymers are composed of polyethylene main chain, poly (ethylene glycol) branch chain and carboxylic side groups, [4][5][6][7][8] and it's convenient to achieve diverse functions and specially solve some problems in concrete engineering because their chemical structure has the potential to be modified. [9][10][11] As an important type of concrete admixture, the main function of superplasticizers is to increase the dispersion of cement paste, [12,13] leading to a low water-to-cement ratio (w/c) and high strength concrete. Compared with other water reducing agents, PCE exhibits excellent water-reducing performance, outstanding slump retention ability, low dosage and wide range of adaptability. [14][15][16][17][18][19][20] More importantly, PCE's performances are able to get breakthrough by means of adjusting and optimizing their molecular structure.The relationship between the structure and performance of PCE is determined by its working mechanism. Recent years, many researches on the working mechanisms of PCE have been carried out, [21][22][23] however, working mechanisms of PCE can hardly be confirmed with certainty at present. The effect of chemical structure of PCE on the dispersion effectiveness is still not sure, and the reason may be that the structure of PCE polymers is complex and changeable. Even so, it is certain that the mechanism behind the dispersion effectiveness of PCE is based on steric hindrance between cement particles as well as electrostatic repulsion forces. [24] Hyperbranched polymer, a kind of highly branched polymer in macromolecule field, has attracted considerable attention because of its remarkable properties, such as high solubility, low viscosity, multifunction, approximately globular three-dime...

An Experimental Assessment of the Water Permeability of Concrete with a Superplasticizer and Admixtures

“…The final goal of using chemical admixtures is to achieve a more durable concrete with self-healing ability [ 25 , 26 ]. Superplasticizers participate in retarding cement hydration and fluidity enhancement [ 27 ], and it has a good dispersing effect on cement paste, as well as a water reduction ratio up to 38.6% [ 28 ].…”

Synthesis and Properties of a Polycarboxylate Superplasticizer with a Jellyfish-Like Structure Comprising Hyperbranched Polyglycerols

“…The initiator for the ring opening polymerization was synthesized from Jeffamine and two equivalents of glycidol, yielding a bis(2,3-dihydroxypropyl) adduct with four terminal hydroxyl groups. 25 This reaction was quantitative, and the formation of the product was confirmed by 1 H/ 13 C NMR spectroscopy (see Figures S6 and S7).…”

“…This derivatization was performed under highly alkaline conditions using an excess of sodium chloroacetate (1.7-fold relative to the hydroxyl groups) to ensure a high degree of substitution. Successful introduction of the carboxymethyl functionalities was evidenced by 13 C NMR spectroscopy via the signals for the carboxylate group at δ = 177.7 ppm and the carbon atom next to it at δ = 76.9 ppm (see Figure S12). Additionally, the FT-IR spectrum of Jeff(hyp.PG)(COOH) n showed characteristic absorption bands at 1597 and 1413 cm −1 , which can be attributed to the asymmetric and symmetric CO stretching vibration of the carboxylate group, respectively (Figure 1).…”

“…12 Similar results were also reported for PCEs with a branched topological structure synthesized by free radical copolymerization of acrylic acid, polyethylene glycol methallyl ether (HPEG), and a branched monomer, which was prepared in a two-step synthesis from diallylamine, methyl acrylate, and trimethylolpropane. 13 Even the incorporation of branched lateral chains into comb-shaped PCEs can effectuate a higher steric hindrance effect as was demonstrated by Li and co-workers. 14 They found that the dispersing performance of IPEG-PCEs was considerably improved after the introduction of hyperbranched polyamidoamine side chains synthesized from ethylene diamine and methyl acrylate.…”

“…NMR and FT-IR Analysis. 1 H and 13 C NMR spectra were recorded on an AVANCE-III 400 MHz NMR spectrometer (Bruker BioSpin GmBH, Karlsruhe, Germany). The chemical shifts were referenced to the residual nondeuterated solvent signal (D 2 O: 1 H NMR δ = 4.79 ppm).…”