Polyelectrolyte multilayers are versatile materials that are used in a large number of domains, including biomedical and environmental applications. The fabrication of polyelectrolyte multilayers using the layer-by-layer technique is one of the simplest methods to obtain composite functional materials. The properties of the final material can be easily tuned by changing the deposition conditions and the used building blocks. This review presents the main characteristics of polyelectrolyte multilayers, the fabrication methods currently used, and the factors influencing the layer-by-layer assembly of polyelectrolytes. The last section of this paper presents some of the most important applications of polyelectrolyte multilayers, with a special focus on biomedical and environmental applications.
Composite solid surfaces
with high content of functional groups
(FGs) are useful materials in different types of applications requiring
stimuli-responsive “hard/soft” architectures, their
improved properties rising from the combination of organic–inorganic
parts. Among different types of weak polyelectrolytes, poly(ethyleneimine)
(PEI) is of great interest in the construction of composite systems
with thin layer-by-layer (LbL) organic films due to the large number
of amino groups per unit mass of polymer. Herein, the spherical silica
microparticles were modified with linear (L) or branched (B) PEI chains
using LbL deposition of a copper complex (PEIL–Cu2+ or PEIB–Cu2+) and poly(acrylic acid) (PAA), glutaraldehyde
selective cross-linking, followed by copper and PAA extraction from
the multilayer. The newly formed silica/(PEIL)10 and silica/(PEIB)10 composites were used in batch and column sorption/desorption
experiments of four heavy metal ions (Cu2+, Ni2+, Co2+, and Cd2+). In noncompetitive conditions
([FG]/Σ[M2+] > 9), all heavy metal ions were retained
on composites, demonstrating the potential application of the prepared
functional microparticles in surface water treatment. However, in
competitive conditions ([FG]/Σ[M2+] < 9), only
Cu2+ is sorbed in high amount (∼2.5 mmol·g–1 PEI) on composites, with simultaneous displacement
of already sorbed ions, demonstrating the solid-phase extraction and
chromatographic properties of the synthesized silica/(PEIL)
n
and silica/(PEIB)
n
composites.
Polybetaines, that have moieties bearing both cationic (quaternary ammonium group) and anionic groups (carboxylate, sulfonate, phosphate/phosphinate/phosphonate groups) situated in the same structural unit represent an important class of smart polymers with unique and specific properties, belonging to the family of zwitterionic materials. According to the anionic groups, polybetaines can be divided into three major classes: poly(carboxybetaines), poly(sulfobetaines) and poly(phosphobetaines). The structural diversity of polybetaines and their special properties such as, antifouling, antimicrobial, strong hydration properties and good biocompatibility lead to their use in nanotechnology, biological and medical fields, water remediation, hydrometallurgy and the oil industry. In this review we aimed to highlight the recent developments achieved in the field of biomedical applications of polybetaines such as: antifouling, antimicrobial and implant coatings, wound healing and drug delivery systems.
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