浅谈提高混凝土抗渗性的对策

根据多年从事混凝土抗渗检验工作的实际经验,就提高混凝土的抗渗性能,提出了几项建议,并对此进行了阐述,为今后如何改善和提高抗渗混凝土的技术性能提供经验借鉴。

Kinetics of Vinyl Chloride Polymerization with Mixture of Initiators

Kinetic models for the rate constants of vinyl chloride polymerization in the presence of initiator mixtures were proposed. They may be used to design the initiator recipes for the vinyl chloride polymerization with uniform rate at different temperatures at which various grades of poly(vinyl chloride) will be prepared.

Research on the Mechanism of Accelerator for Photocurable Resin in 3D Printing

The photopolymerization kinetics of cycloaliphatic epoxide and oxetane with accelerators were investigated with Real-time Fourier transform infrared spectroscopy(RT-FTIR).The consumption rates of epoxy group and oxetane group as a function of time were obtained by monitoring of the absorption peaks in the 789 cm-1 and 981 cm-1.The effect of accelerators type and the accelerating mechanism were discussed.In general,benzyl alcohol and its analogues with electron-donating substituents are useful accelerators for the cationic polymerization of cycloaliphatic epoxide and oxetane.Activated monomer mechanism and free-radical chain-induced decomposition of onium salt cationic photoinitiator account for the observed accelerating effect on the polymerization rate.

Biphenyl Bis [π-cyclopentadienyl ） iron] Dication as an Efficient Cationic Photoinitiator for Epoxy Polymerization

Ferrocenium monocations as photoinitiators for cationic photopolymerization suffer from a limitation of low absorption and low reactivity under high-pressure Hg lamp. Here, a ferrocenium dication salt, biphenyl bis [π-cyclopentadienyl）iron] hexafluorophosphate （[bis（Cp-Fe）-biphenyl] （PF6）2 was synthesized by the ligand exchange reaction between ferrocene and biphenyl. The chemical structure was characterized with FTIR and ^1HNMR. The separation of ferrocenium monocation cyclopentadien-iron-biphenyl hexafluorophosphate （[Cp-Fe-biphenyl] PF6） and dication [bis（Cp-Fe）-biphenyl] （PF6）2 was carried out by column chromatography. The photoactivity of initiating photopolyinerization of epoxide ER14221 was studied as a cationic photoinitiator. [Bis（Cp-Fe）-biphenyl] （PF6）2 can efficiently absorb radiation above 300nm and its photoactivity is higher than that of its monocation.

Desulfurization Mechanism of Cysteine in Synthesis of Polypeptides

The free-radical-based selective desulfurization of cysteine residue is an efficient protocol to achieve ligations at alanine sites in the synthesis of polypeptide and proteins. In this work, the mechanism of desulfurization process has been studied using the density functional theory methods. According to the calculation results, the desulfurization of the thiol group occurs via a three-steps mechanism： the abstraction of hydrogen atom on the thiol group with the radical initiator VA-044 （2,2＇-azobis[2-（2-imidazolin-2-yl）propane]dihydrochloride）, the removal of S atom under the reductant TCEP （tris（2-carboxyethyl）phosphine）, and the formation of RH molecule （with the regeneration of RS radical）. The second step （desulfurization step） is the rate-determining step, and the adduct t-BuSH facilitates the desulfurization of cysteine via benefiting the formation of the precursor of the desulfurization step.

Synthesis and Properties of Novel Surface Active Maleic Monomer Containing Phosphate Group

A novel surface active monomer （surfmer） containing poly（ethylene glycol） chain and terminated phosphate group was synthesized. The copolymerization of synthesized surfmer with NVP （N-vinylpyrrolidone） and with NVP and VEP （5-tert-butylperoxy-5-methyl-2-hexene-3-yne monomer） led to formation of corresponding surface-active copolymers. The capability of application of resulted copolymers as surface active macroinitiators of emulsion polymerization of styrene and as components of polymeric scaffolds was investigated.

Novel acid initiators for the rapid cationic polymerization of styrene in room temperature ionic liquids

Cationic polymerization of styrene has been achieved using several novel acidic initiators in room temperature ionic liquids (ILs) under mild reaction conditions to obtain polymers of low molecular weight with narrow polydispersity. Both strong protic acids such as bis(trifluoromethanesulfonyl) amide acid (HTFSA) and a moderately weak acid such as bisoxalato phosphorous acid (HBOP) have been studied as initiators. It has been observed that HTFSA initiates the polymerization rapidly even at room temperature and below, as compared to HBOP which produces a slower polymerization requiring elevated temperatures to complete. The relative difference in reactivity of the initiators as compared to the previously described HBOB initiator is discussed in terms of the difference in their proton acidity and the consequential basicity of the anions. The efficiency of different ILs as the reaction solvent is also presented.

Graft polymerization of 2-hydroxyethyl methacrylate via ATRP with poly(acrylonitrile-co-p-chloromethyl styrene) as a macroinitiator

Amphiphilic graft copolymers are excellent additives for the development of antifouling membranes by nonsolvent induced phase separation. We report a convenient approach to the synthesis of novel graft copolymers with hydrophobic polyacryloni- trile (PAN) backbones and hydrophilic poly(2-hydroxyethyl methacrylate) (PHEMA) side chains. Atom transfer radical polymerization (ATRP) of 2-hydroxyethyl methacrylate was carried out with poly(acrylonitrile-co-p-chloromethyl styrene) (PAN-co-PCMS) as a macroinitiator in the presence of CuC1/2,2'-bipyridine at 50 ~C in dimethyl sulfoxide. Kinetics of the graft polymerization was also evaluated. The synthesis of poly(acrylonitrile-co-p-chloromethyl styrene-g-2-hydroxyethyl methacrylate) (PAN-co-(PCMS-g-PHEMA)) can be relatively controlled when CMS (the ATRP sites) unit in the macroinitia- tor is around 5 mol%. Both the macroinitiators and graft copolymers were characterized by FTIR, NMR and GPC. The surface morphology and wettability of the copolymer films were studied by AFM and water contact angle measurement, respectively. We demonstrate that phase segregation between the PAN-co-PCMS backbones and the PHEMA side chains takes place and the surface hydrophilicity of the graft copolymers increases with the length of the PHEMA side chains. Because these am- phiphilic graft copolymers can be synthesized in mass, they will be useful as latent additives for the fabrication of advanced PAN separation membranes.