Abstract Compared with the single polymer micelle system, the polyion complex micellar system is consisted of two or more polymers with different composition, which has more flexible structural adjustment and better performance, making them widely used in drug control release. In this work, two azobenzene‐based amphiphilic copolymers P (MMA‐ co ‐PEGMA‐ co ‐NIPAM‐ co ‐HAZOMA) with ionized carboxyl and P (MMA‐ co ‐PEGMA‐ co ‐NIPAM‐ co ‐NNAZOMA) with protonated tertiary amine group were synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization. We studied self‐assembled behavior of polymers and multi‐component polymers, including their multiple responsiveness and the encapsulation, controlled release properties of polyion complex micelle. Light, pH, temperature, and reduction responsiveness of three micelles were investigated by UV–vis spectroscopy, transmission electron microscope (TEM), and dynamic light scattering. Compared to RCP 1, and RCP 2, RCP 1/RCP 2 micelle can release Nile red in both acidic and alkaline environment. When temperature reached critical solution temperature, RCP 1/RCP 2 micelle would release Nile red faster. Polyion complex micelle had better release performance compared to single micelles at the same environment, and could release in a wider range pH, making it had more potential applications in biological science field.
In this article, we introduce a pH-responsive charge-reversible and photo-crosslinkable polymer nanoparticle. It is prepared via typical self-assembly from a block copolymer poly((7-(4-vinyl-benzyloxyl)-4-methylcoumarin)-co-acrylicacid)-b-poly((2-dimethylamino) ethyl methacrylate)-co-styrene) (P(VBMC-co-AA)-b-P(DMAEMA-co-St)), whose two blocks have different ionizable moieties. In an aqueous solution of pH ≤ 4, the cationic polymer nanoparticles are formed due to the fully protonated PDMAEMA. At a pH ranging from 5.0 to 7.8, partially ionized PAA and protonated PDMAEMA lead to the formation of polymer nanoparticles with a mixed shell. In a pH range of 8-10, a large amount of precipitation is produced within the isoelectric point (IEP) region because of the weak hydrophilic two blocks. In an aqueous solution of pH ≥ 10, polymer nanoparticles are reformed with PAA shell and P(DMAEMA-co-St) core. The coumarin groups of polymer can undergo photo-crosslinking and photo-cleavage reactions under UV light irradiation at λ = 365 nm and λ = 254 nm, respectively. The reversible nature of the photo-reaction can regulate the reversal of polymer nanoparticles. Furthermore, the aggregation-induced fluorescence emission (AIFE) property of polymer nanoparticles at different pH is tested by fluorescence emission spectra. The results indicate that the aggregation state of coumarin blocks in solution also changes with the pH value. The DOX release experiment in vitro shows that the release behavior of DOX-loaded nanoparticles can be adjusted by pH and light to achieve significant control. The inhibitory effect on the growth of tumor cells is displayed by cellular uptake and cytotoxicity test in vitro. The self-assembly system of polymer nanoparticles can be cooperatively controlled by multiple stimulations and displays potential applications in controlled drug delivery.
A novel halogen-free 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO)-containing co-curing agent, 6,6′-(1,4-phenylenebis(((4-(phenylamino)phenyl)amino)methylene))bis(dibenzo[c,e][1,2]oxaphosphinine 6-oxide) (DPN) was synthesized via a simple 1-pot or 2-step procedure with yield of 86.2% and 70.8%, respectively. The molecular structures of 4,4′-((1,4-phenylenebis(methanylylidene))bis(azanylylidene))bis(N-phenylaniline) (DPN intermediate) and DPN are characterized by FTIR, NMR, and MS. TGA tests show that the char yield of DPN/EP composites raises to 30.9% when the molar ratio of DPN to 4,4-diaminodiphenyl methane(DDM) is 20:80. Tg values of DPN/EP composites tested by DSC and DMA are similar to neat epoxy resin (EP), which is due to the secondary amine in DPN that participates in the cross-linking reaction of epoxy resin. The storage modulus in the rubber stage (E′-190 °C) of flame-retardant epoxy resin is close to that of neat EP, while their tanδ's are lower, which indicates the similarity of samples' cross-linking density due to the participation of DPN in the cross-linking reaction. The results show that when the molar ratio of DPN and DDM is 5:95, the epoxy has a higher Tg value and better mechanical properties than other samples. The introduction of DPN efficiently improves the flame-retardant properties of epoxy resin with V-0 rating of UL-94 vertical burning test, non-dripping, 41% of limit oxygen index (LOI) value, low peak heat release rate (PHRR), and total heat release (THR).
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