The dispersion RAFT polymerizations mediated with monofunctional and bifunctional macro-RAFT agents were comparatively studied, in which different block copolymer morphologies were detected.

We identified a barely noticed contributor, submarine groundwater discharge (SGD), to acidification of a coastal fringing reef system in Sanya Bay in the South China Sea based on time-series observations of Ra isotopes and carbonate system parameters. This coastal system was characterized by strong diel changes throughout the spring to neap tidal cycle of dissolved inorganic carbon (DIC), total alkalinity, partial pressure of CO2 (pCO2) and pH, in the ranges of 1851-2131 μmol kg(-1), 2182-2271 μmol kg(-1), 290-888 μatm and 7.72-8.15, respectively. Interestingly, the diurnal amplitudes of these parameters decreased from spring to neap tides, governed by both tidal pumping and biological activities. In ebb stages during the spring tide, we observed the lowest salinities along with the highest DIC, pCO2 and Ra isotopes, and the lowest pH and aragonite saturation state. These observations were consistent with a concurrent SGD rate up to 25 and 44 cm d(-1), quantified using Darcy's law and (226)Ra, during the spring tide ebb, but negligible at flood tides. Such tidal-driven SGD of low pH waters is another significant contributor to coastal acidification, posing additional stress on coastal coral systems, which would be even more susceptible in future scenarios under higher atmospheric CO2.

Doubly thermo-responsive triblock copolymer nanoparticles are prepared by a dispersion RAFT polymerization and the nanoparticles exhibit a two-step phase-transition with increasing temperature.

An automated analyzer was developed to achieve fast, precise, and accurate measurements of seawater total alkalinity (A T ) based on single-point titration and spectrophotometric pH detection. The single-point titration was carried out in a circulating loop, which allowed the titrant (hydrochloric acid and bromocresol green solution) and a seawater sample to mix at a constant volume ratio. The dissolved CO 2 in the sample−titrant mixture was efficiently removed by an inline CO 2 remover, which consists of a gas-permeable tubing (Teflon AF2400) submerged in a sodium hydroxide (NaOH) solution. The pH of the mixture was then measured with a custom-made spectrophotometric detection system. The analyzer was calibrated against multiple certified reference materials (CRMs) with different A T values. The analyzer features a sample throughput time of 6.5 min with high precision (±0.33−0.36 μmol kg −1 ; n = 48) and accuracy (−0.33 ± 0.99 μmol kg −1 ; n = 10). Intercomparison to a traditional open-cell A T titrator showed overall good agreement of 0.88 ± 2.03 μmol kg −1 (n = 22). The analyzer achieved excellent stability without recalibration over 11 days, during which time 320 measurements were made with a total running time of over 40 h. Because of its small size, low power consumption requirements, and its ability to be automated, the new analyzer can be adapted for underway and in situ measurements. ■ INTRODUCTIONAs a measure of seawater buffering capacity, total alkalinity (A T ) of a seawater sample is defined as "the number of moles of hydrogen ion equivalent to the excess of proton acceptors (bases formed from weak acids with a dissociation constant K ≤ 10 −4.5 at 25°C and zero ionic strength) over proton donors (acids with K > 10 −4.5 ) in 1 kg of sample". 1 Observations of A T are extremely useful in identifying and assessing physical and biogeochemical processes in the ocean, such as inventory of anthropogenic CO 2 , calcification by shell-building organisms, dissolution/precipitation of calcium carbonate minerals, aerobic versus anaerobic respiration, and water mixing.2−6 As one of the four primary parameters of the marine CO 2 system, A T can be used with one of the other three parameters, pH, pCO 2 , and total dissolved inorganic carbon (DIC), to fully characterize the seawater−carbonic system through thermodynamic calculations. 7,8 In many ocean carbon studies, the required precision and accuracy of seawater A T measurements are stringent (<0.2%) because of the high background values (mean seawater A T ∼ 2300 μmol kg −1 ) compared to relatively small natural variations.The traditional method for high-precision, high-accuracy measurements of seawater A T involves a multi-point potentiometric titration in an open or a closed cell.9,10 It uses a stepwise addition of a strong acid [hydrochloric acid (HCl)] to a known amount of seawater in a titration cell. The titration is monitored using a pH electrode, and the A T is computed from the equivalence point located by a nonlinear least-squares or Gran fun...

The micellar macro-RAFT agent-mediated dispersion polymerization of styrene in the methanol/water mixture is performed and synthesis of temperature-sensitive ABC triblock copolymer nanoparticles is investigated. The thermoresponsive diblock copolymer of poly(N,N-dimethylacrylamide)block-poly[N-(4-vinylbenzyl)-N,N-diethylamine] trithiocarbonate forms micelles in the polymerization solvent at the polymerization temperature and, therefore, the dispersion RAFT polymerization undergoes as similarly as seeded dispersion polymerization with accelerated polymerization rate. With the progress of the RAFT polymerization, the molecular weight of the synthesized triblock copolymer of poly(N,N-dimethylacrylamide)-block-poly[N-(4-vinylbenzyl)-N,N-diethylamine]-b-polystyrene linearly increases with the monomer conversion, and the PDI values of the triblock copolymers are below 1.2. The disper-sion RAFT polymerization affords the in situ synthesis of the triblock copolymer nanoparticles, and the mean diameter of the triblock copolymer nanoparticles increases with the polymerization degree of the polystyrene block. The triblock copolymer nanoparticles contain a central thermoresponsive poly [N-(4-vinylbenzyl)-N,N-diethylamine] block, and the soluble-toinsoluble phase-transition temperature is dependent on the methanol content in the methanol/water mixture.

A new and efficient strategy to synthesize multicompartment block copolymer nanoparticles (MCBNs) by two macro-RAFT agents comediated dispersion polymerization is proposed. By simultaneously employing two macro-RAFT agents in dispersion RAFT polymerization, one-pot synthesis of well-defined MCBNs constructed with two diblock copolymers of poly(tert-butyl methyl acrylate)-block-polystyrene (PtBMA-b-PS) and poly[N-(4-vinylbenzyl)-N,N-diethylamine]-block-polystyrene (PVEA-b-PS) is achieved. These MCBNs contain a PS core and discrete PVEA and/or PtBMA nodules on the PS core. By changing the ratio of the two macro-RAFT agents or the polymerization degree of the solvophobic block in the two diblock copolymer mixture, the structure of MCBNs can be tuned. Our strategy overcomes the inconvenience and difficulty in synthesis of MCBNs, and it introduces a valid way to prepare well-defined MCBNs constructed with two or more diblock copolymers.

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