We developed a facile synthesis for a series of multifunctionalized polyesters by Passerini three-component polymerization (Passerini-3CP) in a “one-pot” method at room temperature using serial dicarboxylic acids, dialdehyde, and tert-butyl isocyanide as monomers. First, the effects of monomer feed ratio, monomer concentration, and different dicarboxylic acids involved in the polymerization were systematically investigated. The in situ FTIR and GPC measurements have suggested a step-growth mechanism for Passerini-3CP. Second, five succinic acid end-capped polyethylene glycols (S-PEGs) with different molecular weights of 400, 800, 1000, 2000, and 4000 g/mol were prepared and selected as dicarboxylic acids for the subsequent Passerini-3CP to fabricate the thermosensitive and biocompatible polyesters. Among the five resulting polyesters, four polyesters from S-PEG-400, S-PEG-800, S-PEG-1000, and S-PEG-2000 show reversible response to the external temperature, and the lower critical solution temperature (LCST) in water is in the range of 28.5–84.2 °C. Through the copolymerization of S-PEG-400 and S-PEG-800, the LCSTs for functional polyesters can be conveniently controlled to be 38.7, 42.3, and 58.0 °C, respectively. After 24–72 h of incubation in polyester solution, the viability rate of HeLa cells reached up to 80–107%, showing its excellent biocompatibility. The cleavable polyesters were also prepared by integrating S–S bonds onto their backbones in Passerini-3CP of 3,3′-dithiodipropionic acid as one comonomer for the biomedical applications. With the aid of the hydrophobicity of doxorubicin (DOX) and thermosensitivity of polyesters, the doxorubicin-loaded carriers with the size of 200–400 nm and core–shell structure were easily obtained by dialysis below LCST and subsequent heating to LCST. The effective release of DOX from the carriers can be triggered by the characteristic reaction of l-glutathione (GSH) with S–S bonds in the functionalized polyester backbones.
A series of multifunctionalized polyamides were facilely prepared by Ugi four‐component polymerization (Ugi‐4CP) in one‐pot method at room temperature using several diacids, aldehydes, 1,4 bis‐(3‐aminopropyl) piperazine and tert‐butyl isocyanide as monomers. The simple combination of monomers in Ugi‐4CP led to formation of nine thermosensitive polyamides in water, and their lower critical solution temperatures (LCSTs) were in range of 13.1‐70.1°C. The LCSTs for the subsequently‐quaternized polyamides (PBA‐800‐Br, PIA‐800‐Br and PCA‐800‐Br) were easily readjusted to the desired value in the inorganic salt solutions. PBA‐800‐Br and PIA‐800‐Br exhibited high antibacterial activity against Gram negative E. coli and Gram positive S. aureus. Confocal laser scanning microscope (CLSM) manifested the clear internalization into the cellular inside for the fluorescent molecule‐labelled polyamides. After 24–72 hours of incubation in polyamide solution, the viability rate of HeLa cells reached up to 80–141%, indicating the excellent biocompatibility. In conclusion, the thermosensitive, antibacterial and biocompatible polyamides have great potential to be used as biomaterials.
In the synthesis of traditional AIE-active polymers with conjugate or multi-benzene system, the troublesome process is still faced such as consuming time, high temperature, catalysis, no water or vacuum, and so on. In this study, the polydihydropyrimidone derivatives ( PDPMDs) with AIE properties are facilely synthesized by the introduction of 4-dihydropyrimidone rings onto non-AIE-active intermediate polyureas (PUs) in Biginelli reaction. It is found that the unsymmetrical L-lysine ethyl diisocyanate and butylenediamine played a very important role in the smooth preparation and fluorescence enhancement of PDPMDs. Compared with the intermediate PUs, the fluorescence of PDPMDs is significantly enhanced (35-fold increase), which is mainly due to the intramolecular aggregation of dihydropyrimidone rings on PUs chains. At the same time, with the increase of the content of dihydropyrimidone rings, the fluorescence intensity of PDPMDs also increases, and the emission wavelength shows an obvious red shift.
In this study, two simultaneous MALI and Ugi polymerizations in one‐pot was performed by combining binary amines, glutaraldehyde, mercaptoacetic acid and t‐butylisonitrile into one four‐component reaction system. The resulting poly(4‐thiazolidinone‐amide)s (PTZAs) contains both thiazolidinone rings from MALI reaction and amide/thiol groups from Ugi reaction, respectively. Unexpectedly, the strong fluorescence emission at 500 nm of PTZA‐E solution is observed under the excitation of 378 nm, which is attributed to the intramolecular “aggregation” of thiazolidinone rings and amide/thiol groups. And also, PTZAs solution showed an excellent aggregation‐induced emission (AIE) by the clusterization‐triggered emission (CTE) mechanism when adding different amount of precipitant. More interestingly, Fe3+ ion violently quenched the fluorescence of PTZA‐E via the redox reaction and spectrum overlaps, and the limit of detection (LOD) of PTZA‐E to Fe3+ ion was measured as 10−4 mol/L. In brief, the two simultaneous polymerizations in one pot provide a great possibility for the polymer with special structure and performance, also including the direct synthesis of AIE‐active polymers from the accessible non‐AIE monomers.
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