Synthesis of end‐functionalized poly(methyl methacrylate) by ruthenium‐catalyzed living radical polymerization with functionalized initiators

A series of functionalized 2‐bromoisobutyrates and 2‐chloro‐2‐phenylacetates led to α‐end‐functionalized poly(methyl methacrylate)s in Ru(II)‐catalyzed living radical polymerization; the terminal functions included amine, hydroxyl, and amide. These initiators were effective in the presence of additives such as Al(Oi‐Pr)₃ and n‐Bu₃N. The chlorophenylacetate initiators especially coupled with the amine additive gave polymers with well‐controlled molecular weights (M_w/M_n = 1.2–1.3) and high end functionality (F_n ～ 1.0). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1937–1944, 2002     

Iron‐catalyzed living radical polymerization of acrylates: Iodide‐based initiating systems and block and random copolymerizations

A half‐metallocene iron iodide complex [Fe(Cp)I(CO)₂] induced living radical polymerization of methyl acrylate (MA) in conjunction with an iodide initiator [(CH₃)₂C(CO₂Et)I, 1 ] and Al(Oi‐Pr)₃ to give polymers of controlled molecular weights and narrow molecular weight distributions (MWDs) (M_w/M_n < 1.2). With the use of chloride and bromide initiators, the MWDs were broader, whereas the molecular weights were similarly controlled. Other acrylates such as n‐butyl acrylate (nBA) and tert‐butyl acrylate (tBA) can be polymerized with 1 /Fe(Cp)I(CO)₂ in the presence of Ti(Oi‐Pr)₄ and Al(Oi‐Pr)₃, respectively, to give living polymers. The 1 /Fe(Cp)I(CO)₂ initiating system is applicable for the synthesis of block and random copolymers of acrylates (MA, nBA, and tBA) and styrene of controlled molecular weights and narrow MWDs (M_w/M_n = 1.2–1.3). © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2033–2043, 2002     

Further evidence of the vibronic coupling of pyrazine as revealed by preresonance raman effect

The excitation wavelength dependences of the intensities of the Raman lines of pyrazine have been measured. The intensity enhancement of the non-totally symmetric Raman line at 925 cm^?1 provided firm evidence of the vibronic coupling between the lowest ¹B_3u(n,π^*) and second lowest ¹B_2u(π,π^*) states. The excitation wavelength dependences of other non-totally symmetric Raman lines suggest also the various vibronic coupling schemes.     

Ruthenium‐catalyzed fast living radical polymerization of methyl methacrylate: The R?Cl/Ru(Ind)Cl(PPh3)2/n‐Bu2NH initiating system

A fast living radical polymerization of methyl methacrylate (MMA) proceeded with the (MMA)₂? Cl/Ru(Ind)Cl(PPh₃)₂ initiating system in the presence of n‐Bu₂NH as an additive [where (MMA)₂? Cl is dimethyl 2‐chloro‐2,4,4‐trimethyl glutarate]. The polymerization reached 94% conversion in 5 h to give polymers with controlled number‐average molecular weights (M_n's) in direct proportion to the monomer conversion and narrow molecular weight distributions [MWDs; weight‐average molecular weight/number‐average molecular weight (M_w/M_n) ≤ 1.2]. A poly(methyl methacrylate) with a high molecular weight (M_n ～ 10⁵) and narrow MWD (M_w/M_n ≤ 1.2) was obtained with the system within 10 h. A similarly fast but slightly slower living radical polymerization was possible with n‐Bu₃N, whereas n‐BuNH₂ resulted in a very fast (93% conversion in 2.5 h) and uncontrolled polymerization. These added amines increased the catalytic activity through some interaction such as coordination to the ruthenium center. © 2002 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 617–623, 2002; DOI 10.1002/pola.10148     

Synthesis of end-functionalized polystyrenes with organosilicon end-capping reagents via living cationic polymerization

The end-functionalization of living polymers with bases (methanol, benzylamine, diethyl sodiomalonate, and sodium methoxide) and organosilicon compounds [X ? Si(CH₃)₃;X ? : CH₂?C(CH₃)COO? , CH₃COO? , CH₂?CHCH₂? , C₆H₅? ] was investigated in the living cationic polymerization of styrene initiated with the 1-phenylethyl chloride/SnCl₄/nBu₄NCl system in CH₂Cl₂ at ?15°C. The four bases and C₆H₅SiMe₃, independent of their structures, were apparently incapable of reacting with the living end and invariably led to polystyrenes with the ω-end chlorine [～ ～ ～ CH₂CH(Ph)Cl] originated from the initiating system. The number-average end-functionality (F?_n) of the chloride, determined by ¹H-NMR, was close to unity (F?_n > 0.9). The presence of chlorine in the polymer was also confirmed by elemental analysis. In contrast, the quenching by the trimethylsilyl compounds with X = methacryloxy, acetoxy, and allyl gave ω-end-functionalized polystyrenes with the corresponding terminal groups (X) for which the F?_n values were close to unity (F?_n > 0.9). The effects of the structure of silyl compounds on end-capping are also discussed. © 1994 John Wiley & Sons, Inc.     

Professor Fosong Wang on his 80th birthday: A great scientist and a great ambassador

It is a great pleasure for international colleagues in polymer science to celebrate Professor Fosong Wang on his 80th birthday. Professor Fosong Wang, a member of the Chinese Academy of Sciences, is a great polymer scientist, with over 300 publications and a few books. He is internationally recognized in his work on stereoregular polymers and electronically active polymers, particularly the development of     

Variable Lebesgue norm estimates for BMO functions. II

The paper concerns characterization of BMO in terms of Banach function spaces. In particular, we are interested in characterizing BMO by using the variable Lebesgue norm.     

Radical polymerization of trifluoromethyl‐substituted methyl methacrylates and their application for use in pressure‐sensitive paint

Three CF₃‐substituted methyl methacrylates (MMAs), 2,2,2‐trifluoroethyl methacrylate (TFEMA), 1,1,1,3,3,3‐hexafluoroisopropyl methacrylate (HFIPMA) and nonafluoro‐tert‐butyl methacrylate (NFTBMA), were polymerized by conventional radical polymerization to give oxygen‐permeable polymers for application in pressure‐sensitive paint (PSP). The radical copolymerizations of styrene with TFEMA, HFIPMA, or NFTBMA were carried out to examine the effect of CF₃ groups on the polymerizability. The e values increased in the order of MMA (0.40) < TFEMA (0.76) < HFIPMA (1.19) < NFTBMA (1.31). The homopolymers of TFEMA, HFIPMA and NFTBMA (PTFEMA, PHFIPMA, and PNFTBM, respectively) were examined as polymers for use in PSP using 5,10,15,20‐tetrakis(pentafluorophenyl)porphinato platinum(II) (PtTFPP). The PSP consisting of PNFTBMA and PtTFPP exerted very high pressure sensitivity and very low temperature sensitivity. In the absence of oxygen, the temperature sensitivity decreased in the order of PTFEMA > PHFIPMA > PNFTBMA = PMMA, which corresponds to the order of glass transition temperatures (T_g). However, the activation energies of the overall process of the luminescence quenching by oxygen were found to be 16.8 (PMMA), 13.0 (PTFEMA), 6.8 (PHFIPMA), and 4.3 kJ mol^?1 (PNFTBMA). Therefore, the low temperature sensitivity of PNFTBMA was attributed to its high degree of substitution with CF₃ groups and to its relatively high T_g value. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 963–972     

INTRAMOLECULAR TRAPPING OF THE NITRENE GENERATED BY PHOTOLYSIS OF S,S-DIPHENYL N-ACYLSULFILIMINE

Abstract

Various N-acyldiphenylsulfilimines (1a-k) were found to undergo photolysis in argon atmosphere, to afford the corresponding isocyanates, diphenyl sulfide and diphenyl disulfide. Attempts to trap intramolecularly the acylnitrene with olefinic linkage or sulfide afforded small amounts of the trapped products, whereas photolysis of N-mesitoyldiphenyl-sulfilimine (Ia) afforded a C–H inserted product of the nitrene in a substantial yield together with the isocyanate. Benzophenone-sensitized photolysis of Ia indicates that the nitrene generated is a singlet species.     

Collision-Induced Dissociation Analysis of Negative Atmospheric Ion Adducts in Atmospheric Pressure Corona Discharge Ionization Mass Spectrometry

Collision-induced dissociation (CID) experiments were performed on atmospheric ion adducts [M + R]^– formed between various types of organic compounds M and atmospheric negative ions R^- [such as O₂ ^–, HCO₃ ^–, COO^–(COOH), NO₂ ^–, NO₃ ^–, and NO₃ ^–(HNO₃)] in negative-ion mode atmospheric pressure corona discharge ionization (APCDI) mass spectrometry. All of the [M + R]^– adducts were fragmented to form deprotonated analytes [M – H]^– and/or atmospheric ions R^–, whose intensities in the CID spectra were dependent on the proton affinities of the [M – H]^– and R^– fragments. Precursor ions [M + R]^– for which R^- have higher proton affinities than [M – H]^– formed [M – H]^– as the dominant product. Furthermore, the CID of the adducts with HCO₃ ^– and NO₃ ^-(HNO₃) led to other product ions such as [M + HO]^– and NO₃ ^–, respectively. The fragmentation behavior of [M + R]^– for each R^– observed was independent of analyte type (e.g., whether the analyte was aliphatic or aromatic, or possessed certain functional groups).