Alternating Sequence Control for Poly(ester amide)s by Organocatalyzed Ring-Opening Polymerization.

Sequence-controlled polymerization is the forefront of polymer chemistry. Herein, the feasibility of sequence regulation by using organocatalyzed ring-opening polymerization (ROP) is demonstrated. In particular, ring expansion strategy is employed to synthesize pre-organized monomers 1 and 2. ROP is conducted by using 1,5,7-triazabicyclo[4.4.0]dec-5-ene and benzyl alcohol as the catalyst and initiator, respectively. Poly(ester amide)s (PEAs) P1-P3 comprising glycolic acid, lactic acid, and 7-aminoheptanoic acid units are obtained in high molecular weights and good yields. NMR and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry results verify the microstructural integrity of P1 and P2. Differential scanning calorimetry results show that PEA without methyl branches is crystalline. Moreover, thermal stability, surface wettability, and degradation profiles of P1-P3 are also investigated.

Hyperbranched Aliphatic Polyester via Cross-Metathesis Polymerization: Synthesis and Postpolymerization Modification.

A novel postpolymerization modification methodology is demonstrated to achieve selective functionalization of hyperbranched polymer (HBP). Terminal and internal acrylates of HBP derived from cross-metathesis polymerization (CMP) are functionalized in a chemoselective fashion using the thiol-Michael chemistries. Model reactions between different thiols (benzyl mercaptan and methyl thioglycolate) and acrylates (n-hexyl acrylate and ethyl trans-2-decenoate) by using dimethylphenylphosphine or amylamine as the catalyst are investigated to optimize the modification protocol for HBP. High-molecular-weight HBP P0 is generated through CMP of AB2 monomer 2, a compound containing one α-olefin and two acrylate metathetically polymerizable groups. CMP kinetics is monitored by NMR and gel permeation chromatography (GPC). Accordingly, microstructural analysis is conducted in detail, and CMP procedure is optimized. Postpolymerization modification of HBP P0 is performed via two distinguished strategies, namely one-step complete modification and sequential modification, to generate terminally and/or internally functionalized HBPs P1-P3 in a chemoselective fashion by using phosphine-initiated and/or base-catalyzed thiol-Michael chemistries. Finally, thermal stability and glass transition behaviors of HBPs P0-P3 are studied by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC), respectively.

[Simultaneous determination of lignans and organic acids in Schisandrae Chinensis Fructus by UFLC-Q-TRAP-MS/MS].

An analytical method based on UFLC-QTRAP-MS/MS was developed for simultaneous determination of fifteen components including eleven lignans (schizantherin B, schisandrol B, schizandrin C, γ-schisandrin, deoxyschizandrin, schisantherin, schisandrin, schisanhenol, gomisin D, gomisin J, and angeloylgomisin H) and organic acids (S)-malic acid, D(-)-tartaric acid, protocatechuic acid, and quinic acid) in Schisandrae Chinensis Fructus. Samples from different product specifications were evaluated and analyzed. The chromatographic separation was performed on a Synergi™ Hydro-RP 100Å column (2.0 mm×100 mm, 2.5 µm) at 40 °C with a gradient elution by employing 0.1% aqueous formic acid (A)-acetonitrile (B) as the mobile phase, and the flow rate was 0.4 mL·min⁻¹, using an electrospray ionization (ESI) source and multiple reaction monitoring (MRM) mode. Fifteen components were evaluated synthetically by TOPSIS and gray related degree. The results showed that fifteen components had good linearity (r>0.999 90), and the limits of detection were all satisfactory. The average recoveries of standard addition for the compounds were between 95.42 % and 98.86 %, and the relative standard deviations were less than 5%. The greatest difference of ri in grey related degree was 58.1%, whilst the greatest difference of Ci value in TOPSIS method was 94.8%. The results of these two methods showed that the holistic quality of No. 14 sample was the best. The developed method was accurate and reliable, which was suitable for the simultaneous determination of multiple functional substances and able to provide a new basis for the comprehensive assessment and overall control of the quality of Schisandrae Chinensis Fructus.

[Comparative analysis of multiple index constituents in Ophiopogonis Radix and Liriopes Radix].

An analytical method based on UFLC-QTRAP-MS/MS was established for simultaneous determination of thirty-three components including steroidal saponins, homoisoflavonoids, amino acids and nucleosides in Ophiopogonis Radix. Thirty-three target components of commercial medicinal materials of Maidong were comparative analysis. Synergi™ Hydro-RP 100 column (2.0 mm × 100 mm, 2.5 µm) was used with 0.1% formic acid solution-0.1% formic acid acetonitrile for gradient elution at a flow rate of 0.4 mL·min⁻¹. In addition, multiple reaction monitoring (MRM) mode was employed. The data were comprehensively processed and analyzed with hierarchical clustering analysis(HCA), principal component analysis(PCA) and partial least squares discriminant analysis(PLS-DA) methods. All components showed good linearity(r>0.999 0) within the tested ranges. The average recoveries were between 96.23%-102.0%, and the relative standard deviation(RSD) were less than 5%. The results showed that there were significant differences in components between Ophiopogonis Radix and Liriopes Radix, with seven components obviously different. This method was useful for providing basis for the comprehensive evaluation and intrinsic quality control of Ophiopogonis Radix and Liriopes Radix , and may provide a new method reference for the identification of Ophiopogonis Radix and Liriopes Radix.

Precision Aliphatic Polyesters with Alternating Microstructures via Cross-Metathesis Polymerization: An Event of Sequence Control.

Sequence-regulated polymerization is realized upon sequential cross-metathesis polymerization (CMP) and exhaustive hydrogenation to afford precision aliphatic polyesters with alternating sequences. This strategy is particularly suitable for the arrangement of well-known monomer units including glycolic acid, lactic acid, and caprolactic acid on polymer chain in a predetermined sequence. First of all, structurally asymmetric monomers bearing acrylate and α-olefin terminuses are generated in an efficient and straightforward fashion. Subsequently, cross-metathesis (co)polymerization of M1 and M2 using the Hoveyda-Grubbs second-generation catalyst (HG-II) furnishes P1-P3, respectively. Finally, hydrogenation yields the desired saturated polyesters HP1-HP3. It is noteworthy that the ε-caprolactone-derived unit is generated in situ rather than introduced to tailor-made monomers prior to CMP. NMR and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) results verify the microstructural periodicity of these precision polyesters. Differential scanning calorimetry (DSC) results reflect that polyesters without methyl side groups exhibit crystallinity, and unsaturated polyester samples show higher glass transition temperatures than their hydrogenated counterparts owing to structural rigidity.

Synthesis of nitrogen-doped graphene quantum dots (N-GQDs) from marigold for detection of Fe3+ ion and bioimaging.

Graphene quantum dots (GQDs) are synthesized by the method of high-temperature pyrolysis from marigold granules and subsequently nitrogen-doped graphene quantum dots (N-GQDs) are synthesized from ethylenediamine by hydrothermal treatment, which shows a strong blue emission with 7.84% quantum yield (QY). This will be used in detection of Fe3+ in water environments and the field of bioimaging.