Molecules 2023 , 28 , 7984
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Figure1. Classification of wet-end chemicals.
Over the past several years, intense research on new types of retention aids has resulted in an enormous number of fundamental [8–11] and applied studies [12–15] due to their significant effect on paper stock quality, and the operation efficiency of paper machines. The retention efficiencies of retention aids are of great significance, especially under high shear condition. The appropriate use of retention aids is an effective way to reduce environmental pollution and save resources via the retention of fines and fillers. Spherical polyelectrolyte brushes (SPBs) refer to the system that long polyelectrolyte chains are grafted to colloidal spheres [16]. Recently, it has attracted much attention due to its excellent retention performance in papermaking originating from its core–shell struc- ture [17]. It not only takes the advantage of the ionization surface and three-dimensional nanostructures, but also has the controllable charge density and molecular weight of graft- ing polymer chains [18–20]. Moreover, its spherical symmetry or quasi-symmetric structure has the ability of shear resistance. So the flocs flocculation would be easier to be induced by SPBs though the bridging effect, thus making the flocs stronger in turbulence. Consequently, considered as an effective retention aid, SPBs have a promising application prospect in wet-end papermaking. To date, a series of reviews about retention aids in wet-end papermaking have focused on chitosan [21], cellulose [22], and polymer [23]. As for SPBs, since the first review reported by Ballauff, M., 2007 [24], many published reviews have mainly concentrated on the construction of nanocomposites [25], ionic effects [26] and their application in sustainable energy [27], and nanoreactors [28]. However, there is no review related to SPBs as a retention aid in wet-end papermaking, which is still needed. In this article, recent studies on the retention aids and basic theory of wet-end papermaking are reviewed firstly, including single-component systems and dual-component systems as well as their application on papermaking. Furthermore, the synthesis and application of SPBs in wet-end papermaking, and the interaction of SPBs with calcium carbonate and fibers, are described. Through this review, a new direction in retention aids in wet-end papermaking, where we see great potential for SPBs, is highlighted, emphasizing the structure–function relationship with respect to retention performance. Finally, the existing challenges and development trends of high performance retention aids are proposed and prospected.
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