Facile synthesis and surface activity of poly(ethylene glycol) star polymers with a phosphazene core

Novel Approach for the Synthesis of Chlorophosphazene Cycles with a Defined Size via Controlled Cyclization of Linear Oligodichlorophosphazenes [Cl(PCl2=N)n-PCl3]+[PCl6]. Int J Mol Sci 2021;22:ijms22115958. [PMID: 34073083 PMCID: PMC8199110 DOI: 10.3390/ijms22115958]

Despite a significant number of investigations in the field of phosphazene chemistry, the formation mechanism of this class of cyclic compounds is still poorly studied. At the same time, a thorough understanding of this process is necessary, both for the direct production of phosphazene rings of a given size and for the controlled cyclization reaction when it is secondary and undesirable. We synthesized a series of short linear phosphazene oligomers with the general formula Cl[PCl2=N]n–PCl₃⁺PCl₆^– and studied their tendency to form cyclic structures under the influence of elevated temperatures or in the presence of nitrogen-containing agents, such as hexamethyldisilazane (HMDS) or ammonium chloride. It was established that linear oligophosphazenes are inert when heated in the absence of the mentioned cyclization agents, and the formation of cyclic products occurs only when these agents are involved in the process. The ability to obtain the desired size phosphazene cycle from corresponding linear chains is shown for the first time. Known obstacles, such as side interaction with the PCl₆^– counterion and a tendency of longer chains to undergo crosslinking elongation instead of cyclization are still relevant, and ways to overcome them are being discussed.

The synthesis of thermoresponsive POSS-based eight-arm star poly(N-isopropylacrylamide): A comparison between Z-RAFT and R-RAFT strategies

Z-Type POSS-based eight-arm star poly(N-isopropylacrylamide), POSS-(PNIPAM)₈-Z, is synthesized and demonstrated to be a thermoresponsive switchable emulsifier.

Graphene oxide-polyethylene glycol incorporated PVDF nanocomposite ultrafiltration membrane with enhanced hydrophilicity, permeability, and antifouling performance

The novel highly hydrophilic composite additive, graphene oxide-polyethylene glycol (GO-PEG, further abbreviated as P-GO), was synthesized from GO and PEG by the esterification reaction. Then, P-GO was blended into a polyvinylidene fluoride (PVDF) casting solution as an additive, and the effects of P-GO on the performance of the PVDF ultrafiltration (UF) membrane were researched. When amount of added P-GO was 0.5 wt%, the flux of the resultant modified membrane (denoted as P/0.5P-GO) reached as high as 93 L m^-2·h^-1, that is twice than that of the pure PVDF membrane (45 L m^-2·h^-1). Furthermore, water contact angle results confirmed significantly improved hydrophilicity of the P/0.5P-GO membrane. Results of antifouling tests revealed that the P/0.5P-GO membrane showed the lowest total resistance and irreversible resistance among all the membranes prepared in this study, and after physical cleaning, its flux recovery ratio was the highest-78%. These results demonstrated improved antifouling performance of the P/0.5P-GO membrane. Therefore, it can be concluded that P-GO as an additive material for the PVDF membrane has satisfactory performance in improving the membrane hydrophilicity, permeability, and antifouling performance in practical applications.

Water-soluble Hemin-mPEG-enhanced Luminol Chemiluminescence for Sensitive Detection of Hydrogen Peroxide and Glucose

In the present study, we synthesized a water-soluble substance (Hemin-mPEG) at room temperature by using hemin and poly(ethylene glycol) methyl ether (mPEG). It was found that the Hemin-mPEG maintained the excellent catalytic activity inherited from hemin, and was first used to catalyze a luminol-H₂O₂ chemiluminescence (CL) system to generate an intense and slow CL signal. The results of a mechanism research showed that the presence of Hemin-mPEG could promote the production of oxygen-relative radicals from H₂O₂ and dissolved oxygen in solution. Based on this mechanism, an ultra-sensitive, cheap and simply practical sensor for detecting glucose and H₂O₂ was developed. Under the most optimal experimental conditions, H₂O₂ and glucose detection results exhibited a good linear range from 0.002 to 3 μM and from 0.02 to 4 μM, respectively, and the detection limits were 1.8 and 10 nM, respectively. This approach has been successfully used to detect glucose in actual biological samples, and achieved good results.