RAFT‐Mediated Polymerization‐Induced Self‐Assembly

After a brief history that positions polymerization‐induced self‐assembly (PISA) in the field of polymer chemistry, this Review will cover the fundamentals of the PISA mechanism. Furthermore, this Review will also give an overview of some of the features and limitations of RAFT‐mediated PISA in terms of the choice of the components involved, the nature of the nanoobjects that can be obtained and how the syntheses can be controlled, as well as some potential applications.     

Surface‐initiated nitroxide‐mediated polymerization of sodium 4‐styrene sulfonate from latex particles

In this study, we report the use of a double‐headed dialkoxyamine trithiocarbonate ( I ) capable of acting as chain transfer agent via reversible addition‐fragmentation chain transfer polymerization or as initiator via nitroxide‐mediated polymerization. It is worth mentioning that I was revealed as an effective dual chain transfer agent in the synthesis of multiblock copolymers via bulk and emulsion processes. In this article, we report the employing of I in dispersed systems to obtain amphiphilic multiblock copolymers and latexes. In this case, a water soluble macroagent of PAA previously synthetized was used in disperse media using a mixture of methanol/water (70:30, w/w). Stable latexes were obtained via polymerization‐induced self‐assembly and surface‐initiated polymerization of SSNa from alkoxyamine‐functionalized latex PAA‐b‐PS‐b‐PAA was also obtained © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 437–444     

运用PISA科学素养测评框架探讨高中化学必修教材习题的特征

以人教版和鲁科版化学必修教材的习题为研究对象,基于PISA科学素养测评框架中的2个维度(科学能力、科学情境)对习题的提问方式进行分析。研究发现,2个版本教材有9成以上的习题考查“解释科学现象”能力,而考查“评价和设计科学探究”和“科学地解释证据和数据”能力的习题很少;2个版本教材具有情境的习题不到40%,其中,个人化情境和地区化情境较多,全球化情境较少。卡方检验表明,2个版本教材习题考查的科学能力分布存在显著差异,2个版本教材习题的科学情境分布存在显著差异。     

Exerting Spatial Control During Nanoparticle Occlusion within Calcite Crystals

In principle, nanoparticle occlusion within crystals provides a straightforward and efficient route to make new nanocomposite materials. However, developing a deeper understanding of the design rules underpinning this strategy is highly desirable. In particular, controlling the spatial distribution of the guest nanoparticles within the host crystalline matrix remains a formidable challenge. Herein, we show that the surface chemistry of the guest nanoparticles and the [Ca²⁺] concentration play critical roles in determining the precise spatial location of the nanoparticles within calcite crystals. Moreover, in situ studies provide important mechanistic insights regarding surface‐confined nanoparticle occlusion. Overall, this study not only provides useful guidelines for efficient nanoparticle occlusion, but also enables the rational design of patterned calcite crystals using model anionic block copolymer vesicles.     

Ethylene-Coordinative Chain-Transfer Polymerization-Induced Self-Assembly (CCTPISA)

Block copolymers based on ethylene (E) and butadiene (B) were prepared using the ansa-bis(fluorenyl) complex {Me₂Si(C₁₃H₈)₂Nd(BH₄)₂Li(THF)}₂ in combination with (n-Bu)(n-Oct)Mg (BOMAG) as a chain-transfer agent. The diblock copolymers incorporating a soft poly(ethylene-co-butadiene) segment, called ethylene butadiene rubber (EBR), and a hard polyethylene (PE) one were obtained by simply adjusting the different feeds of monomers during the polymerization. The soluble EBR block was formed first by feeding the catalytic system dissolved in toluene at 70 °C with a mixture of ethylene and butadiene (E/B molar ratio 80 : 20). Then the feeding was stopped leading to the consumption of a large part of the residual monomers. The reactor was finally fed with ethylene to form the PE block. By varying the molar mass of the latter, it is shown that the resulting soft-b-hard block copolymers can self-assemble simultaneously to the growth of the PE block in agreement with a polymerization-induced self-assembly (PISA) mechanism. The self-assembly is discussed considering the reaction conditions, the crystallization of the PE block, and the polymerization mechanism involved.     

Surface functionalized nano‐objects from oleic acid‐derived stabilizer via non‐polar RAFT dispersion polymerization

Surface functionalization in a nanoscopic scaffold is highly desirable to afford nano‐particles with diversified features and functions. Herein are reported the surface decoration of dispersed block copolymer nano‐objects. First, side‐chain double bond containing oleic acid based macro chain transfer agent (macroCTA), poly(2‐(methacryloyloxy)ethyl oleate) (PMAEO), was synthesized by reversible addition‐fragmentation chain transfer (RAFT) polymerization and used as a steric stabilizer during the RAFT dispersion block copolymerization of benzyl methacrylate (BzMA) in n‐heptane at 70 °C. We have found that block copolymer morphologies could evolve from spherical micelles, through worm to vesicles, and finally to large compound vesicles with the increase of solvophobic poly(BzMA) block length, keeping solvophilic chain length and total solid content constant. Finally, different thiol compounds having alkyl, carboxyl, hydroxyl, and protected amine functionalities have been ligated onto the PMAEO segment, which is prone to functionalization via its reactive double bond through thiol‐ene radical reactions. Thiol‐ene modification reactions of the as‐synthesized nano‐objects retain their morphologies as visualized by field emission‐scanning electron microscopy. Thus, the facile and modular synthetic approach presented in this study allowed in situ preparation of surface modified block copolymer nano‐objects at very high concentration, where renewable resource derived oleate surface in the nanoparticle was functionalized. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 263–273