Block copolymers of DMAEMA with 4VP can be synthesized by ATRP.

Hello Rakibul Islam ,

a blockcopolymer of 4VP and DMAEMA can be synthesized by anioniic polymerization starting with 4VP as the first monomer. The P4VP macronanion is able to initiate the polymerization of the PDMAEMA block. There are articles on pentablockcopolymers, which were synthesized by a bifunctional growth of P2VP anions, subsequent growth of the PDMAEMA-blocks and PMMA-blocks afterwards.

You can find the synthetic procedure in one of the references of this article:

Article Highly Tunable Nanostructures in a Doubly pH‐Responsive Pent...

One-pot synthesis of block copolymer dispersant by ICAR ATRP with ppm copper catalyst and the dispersibility on pigment

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https://doi.org/10.1016/j.porgcoat.2022.106914Get rights and content

Abstract

The controlled / living polymerization mechanisms have advantages on synthesizing the dispersant with defined structures and compositions, while encountering with individual drawbacks in industrial application. Based on the initiators for continuous activator regeneration atom transfer radical polymerization (ICAR ATRP) of oligo(ethylene oxide)methyl ether methacrylate (OEEMA) and glycidyl methacrylate (GMA) monomers, the diblock copolymers POEOMA-b-P(OEOEMA-co-GMA) were prepared. The GMA units were further modified with 3-mercaptopropionic acid (MPA) agent. The polymerization and modification procedure can be readily realized in a one-pot technology with complete monomer conversion (~100%) and high ring-opening efficiency (~100%), as well as low concentration copper catalyst (100 ppm). Using the MPA modified P(OEOEMA-co-GMA) as anchoring block, POEOMA as stabilizing block, the obtained block copolymers can be used as dispersant to disperse and stabilize the pigment yellow 14. The standing experiment, optical microscope (OM) and dynamic light scattering (DLS) measurements reached to a consistent conclusion that the absolute number of carboxyl groups on each chain modulate the dispersibility of the dispersions, rather than the relative content of carboxyl groups. This work provided a feasible one-pot technology to efficient dispersants.

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Introduction

The dispersants, acting as indispensable additives, have been widely used in various fields in industry due to the unique property of dispersing and stabilizing particles. For example, the dispersant can be used to disperse the pesticide, [1], [2], [3], [4] the additives in food, [5] the pigment in paint and ink, etc. Up to now, the low molecular weight dispersants have been well studied and extensively used due to the simple preparation and low cost. However, because of the limited anchoring groups and short stabilizing moiety, the application of low molecular weight dispersants was always limited. Alternatively, the polymeric dispersants with high molecular weight and random, block, or graft structures were welcomed. The dispersants with block and graft structures were especially focused due to the excellent dispersibility brought by the well-defined structures, controlled compositions and site-specific functionality. [6], [7], [8], [9] Typically, such copolymers can be synthesized by controlled / living polymerization mechanisms, such as living anionic polymerization (LAP), [10], [11], [12], [13], [14], [15] atom transfer radical polymerization (ATRP), [16], [17], [18], [19], [20] nitroxide mediated radical polymerization (NMRP), [21] reversible addition-fragmentation chain transfer (RAFT) polymerization, [22], [23], [24] group transfer polymerization (GTP), [25], [26] and so on.For example, using the normal ATRP, Auschra et al. prepared the diblock copolymer poly(butylacrylate)-b-poly(dimethylamino ethylacrylate) (PBA-b-PDMAEA) and studied their dispersibility on opaque or transparent pigments. [16] Similarly, Monteiro et al. synthesized the amphiphilic block copolymer methoxy poly(ethylene glycol)-b-poly(4-vinyl pyridine) (mPEG-b-P4VP) by normal ATRP. [17] Comparing with the sodium salt of polyacrylic acid (Na-PAA), the diblock copolymer mPEG-b-P4VP showed excellent dispersibility on TiO2 nanoparticles. The normal ATRP was also used to synthesize the amphiphilic block copolymer poly(acrylic acid)-b-poly(4-vinylpyridine) (PAA-b-P4VP) and poly(acrylic acid)-b-poly(2-(dimethylamino)ethyl methacrylate) (PAA-b-PDMAEMA) by Costa et al., [18] and their application on stabilizing the TiO2 particles was compared. Aiming to meet the requirement for the pigment dispersion in LCD color filters, the block copolymer poly[(2-dimethylamino)ethyl methacrylate]-b-poly[oligo(ethylene oxide)methyl ether methacrylate] (PDMAEMA-b-POEOMA) was designed and synthesized by normal ATRP, [19] and the improved dispersibility on copper phthalocyanine pigment was achieved. Alternatively, using the reverse ATRP, Lokhande et al. synthesized the diblock copolymer poly(butyl methacrylate)-b-poly(glycidyl methacrylate) (PBMA-b-PGMA) and further modified the GMA units with methyl ethanol amine. [20] The generated block copolymers also showed excellent dispersibility on pigments.With versatility on polymerizing plenty of functional monomers, the RAFT mechanism was also widely used to synthesize the dispersants with expected structures and compositions. For example, North et al. prepared the zwitterionic diblock copolymer poly(methacrylic acid)-b-poly(2-(dimethylamino)ethyl methacrylate) (PMAA-b-PDMA) using an atom-efficient, wholly aqueous one-pot technology. [22] The obtained zwitterionic diblock copolymers can be served as highly effective dispersants for transparent yellow iron oxide nanoparticles. Using the RAFT based alcoholic dispersion polymerization, they also synthesized the nano-objects with poly(2-(dimethylamino)ethyl methacrylate) (PDMA) as steric stabilizer block and poly(benzyl methacrylate) (PBzMA) as core-forming block. [23] The nano-objects can be used to disperse the model pigment of silica. Using the RAFT mechanism, Saindane et al. prepared the amphiphilic diblock copolymer poly (ethyl acrylate)-b-poly (acrylic acid) (PEA-b-PAA) and introduced it into water borne coating formulation. [24]With powerful control on the structures and composition of copolymers, the LAP mechanism was also found extensive application in preparing the dispersants. For example, via sequential LAP in tetrahydrofuran (THF) solvent, the block copolymer poly(2-vinylpyridine)-b-poly(ε-caprolactone) (P4VP-b-PCL) was realized and used for dispersing the TiO2 nanoparticle. [10], [11], [12] Using the LAP mechanism, the diblock, triblock and tapered copolymers based on tert-butyl methacrylate (tBMA), ethylene oxide (EO), 4VP, and DMAEMA monomers were synthesized by Creutz et al. [13], [14], [15] By transformation of the tBMA units into sodium methacrylate (MANa) units, the generated copolymers can be employed as effective dispersants for TiO2. The triblock copolymers consisting of PMANa as outer blocks cannot stabilize the dispersion, and the triblock copolymers with the reverse structure form poorly stable dispersions due to partial particle bridging. The stabilization capability was even lost in the case for non-blocky distribution of the DMAEMA and MANa comonomers. Furthermore, they confirmed that the blockiness of comonomer distribution was a prerequisite for expected dispersibility. The tapered diblock with a regular change in composition from one block to the other one has better dispersibility than that for the pure diblock copolymer. The analysis on these model copolymers actually confirmed that the molecular composition of the block copolymers showed important effect on the dispersion stability.Obviously, the above examples illustrated that the block copolymers had been confirmed with excellent dispersibility in pigment formulations. However, the employed mechanisms were always limited with individual drawbacks, such as the deep color of copper catalyst in ATRP, expensive chain transfer agent in RAFT, tedious or strict operation conditions in GTP or LAP mechanisms. In most cases, the complex operations for purification should be accompanied, which increased the cost and lowered the possibility in an industrial application. Thus, the practical application of the block dispersant is still encountering with much challenge and less feasibility. In the past several years, employing a reversible activation and deactivation equilibrium catalyzed by transition-metal redox-active complexes, [27], [28], [29], [30], [31], [32], [33], [34], [35] the normal ATRP process has been updated by using lower concentration (ppm) of copper catalyst, such as initiators for continuous activator regeneration (ICAR) ATRP, [36] activators regenerated by electron-transfer (ARGET) ATRP, [37] supplemental activators and reducing agent (SARA) ATRP, [38] electrochemically mediated ATRP (eATRP), [39], [40] and photo-induced ATRP. [41], [42], [43] With the advantages of ppm copper catalyst, cheap catalyst and initiators, versatile monomers and convenient operations, these techniques are finding with potential application in industry with large scale.In this contribution, aiming to seeking an effective dispersant and exploring a versatile route to their industrial production, the ICAR ATRP with ppm copper catalyst was attempted to target the model diblock copolymer POEOMA-b-P(OEOMA-co-GMA). The carboxyl groups were subsequently introduced by modifying GMA units with 3-mercaptopropanoic acid (MPA) agent via ring-opening reaction (Scheme 1). Especially, a one-pot technology was developed, which was featured with high monomer conversion, simple operations and correspondingly low cost in practical applications. The application of the generated block copolymers as dispersants was comprehensively compared and analyzed.

Section snippets

Materials Glycidyl methacrylate (GMA, 99%, Adamas), and oligo(ethylene oxide) methyl ether methacrylate(OEOMA300, average molecular weight 300, Aldrich) were purchased and passed over a column of basic alumina to remove inhibitor prior to use. Tris(2-pyridylmethyl)amine (TPMA) was synthesized by following the previously reported procedure [44]. Toluene (99%, Greagent), ethanol (99.7%, Greagent), copper(II) bromide (99%, Adamas), ethyl 2-bromoisobutyrate (EBiB, 98%, Adamas), 3-mercaptopropionic acid (MPA,

Synthesis and characterization of MPA modified POEOMA-b-P(OEOEMA-co-GMA) Aiming to prepare the dispersant for yellow 14 in aqueous formulation, the stabilizing block of POEOMA was selected due to the excellent solubility in water. [36], [37], [45] According to the principle for dispersants, [6], [7], [8], [9], [46] the anchoring block containing amine or carboxyl groups was always preferred. However, the acrylic monomer with functional groups, such as amine or carboxyl groups, were difficult to polymerize in an ATRP system, especially in an ATRP system with ppm

Conclusion Using the ICAR ATRP technique, the diblock copolymer POEOMA-b-P(OEOEMA-co-GMA) can be readily synthesized in a one-pot technology in the presence of ppm coper catalyst. The GMA units can be further modified with MPA agent to introduce the carboxyl groups. The polymerization and modification procedure can be performed with complete monomer conversion (~100%) and high efficiency (~100%). No any additional purification procedure is required and the operations is largely simplified. Thus, the

CRediT authorship contribution statement Conceptualization: Meng Luan, Guowei Wang.Methodology: Meng Luan, Ding Shen, Peng Zhou.Software: Meng Luan, Penghan Li, Boyang Shi.Validation: Meng Luan.Formal analysis: Meng Luan, Ding Shen, Di Li.Investigation: Meng Luan, Ding Shen, Peng Zhou, Di Li.Resources: Meng Luan, Ding Shen, Di Li.Data Curation: Meng Luan, Peng Zhou, Boyang Shi.Writing-Original draft: Meng Luan.Writing-Review & editing: Meng Luan, Guowei Wang.Supervision: Guowei Wang.Visualization: Meng Luan, Peng Han, Guowei Wang.

Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement We appreciate the financial support of this research by the National Natural Science Foundation of China (21774022).

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