Fu-Mian Li

Bismaleimides Having Electron-Donating Chromophore Moieties: A New Approach Toward Monitoring the Process of Curing Based on Their Fluorescence Behavior

Bismaleimides having electron-donating diphenylmethylamine or triphenylamine moieties (A (=) -D (*) -A (=) , as well as their saturated model compounds were synthesized. Their fluorescence behavior was found to show a strong fluorescence structural self-quenching effect (SSQE). On the basis of this strong SSQE of A (=) -D (*) -A (=) bismaleimides, a new fluorescence approach can be developed to monitor the curing process in bismaleimide resins, which is in agreement with the results from FT-IR and 1 H NMR analyses.

Multiple morphologies of molecular assemblies formed by polystyrene-block-poly[2-(β-D-glucopyranosyloxy)ethyl acrylate] in water

A variety of molecular assemblies have been prepared from a new kind of amphiphilic diblock copolymer, polystyrene-block-poly[2-(β-D-glucopoyranosyloxy)ethyl acrylate] (PSt-b-PGEA). The morphologies include spheres, vesicles, tubules, porous spheres and large compound vesicles. These molecular assemblies are similar in morphology to the so-called ‘‘crew-cut ’’ aggregates that have been systematically studied by Eisenberg’s group and were prepared in the same manner. The preparation of such molecular assemblies was carried out by first dissolving the copolymer in a common solvent, followed by addition of water to freeze the polystyrene block. The solvents used in this report were N,N-dimethylformamide (DMF), tetrahydrofuran (THF), dioxane and their mixtures. It has been observed that by changing the solvent, or the solvent mixture, different morphologies can be obtained from a single copolymer, and the transformation of these morphologies can be easily adjusted by changing the composition of the solvent mixture. One typical example is the morphological transitions between tubules and vesicles of PSt77-b-PGEA6, which is initially dissolved in mixed THF–DMF solvent. These molecular assemblies contain a high density of glucose moieties on the surface, therefore, they may find applications as cellular-specific drug delivery systems or be used as building blocks for highly ordered supramolecular architectures.

Vinyl monomers bearing chromophore moieties and their polymers. V. Synthesis and fluorescence behavior of a vinyloxy monomer bearing electron-accepting chromophore moiety, N-(2-(vinyloxy)ethyl)-1,8-naphthalimide, and its polymer

A vinyloxy monomer bearing electron-accepting chromophore, N-(2-(vinyl-oxylethyl)-1,8-naphthalimide (VOENI), was synthesized by reaction of potassium 1,8-naphthalimide with 2-chloroethyl vinyl ether. VOENI can be homopolymerized by cationic initiation and copolymerized with maleic anhydride (MAn) under radical initiation. The fluorescence behaviors of VOENI and its polymers were investigated. It has been found that the fluorescence intensity of the VOENI monomer is much lower than that of its polymers at the same chromophore concentration. This means that a structural self-quenching effect (SSQE) has been also observed in the vinyloxy monomer consisting of an electron-accepting chromophore, which has opposite electronic structure in comparison with acrylates bearing electron-donating chromophores as we have reported previously. The SSQE is attributed to the charge-transfer interaction between the electron-accepting chromophore and the electron-donating double bond in the same molecule. The fluorescence quenching of 1,8-naphthalic anhydride and P(VOENI-co-MAn) by ethyl vinyl ether (EVE), dihydrofuran, triethylamine (TEA), etc. evidences that the electron-rich vinyloxy group does act as an important role in the SSQE of VOENI. C 60 can also quench the fluorescence of the polymers, and an upward deviation from the linearity of the Stern-Volmer plot was observed showing that C 60 acted as a powerful electron donor to quench the fluorescence of the copolymer.

A unique synthesis of a well-defined block copolymer having alternating segments constituted by maleic anhydride and styrene and the self-assembly aggregating behavior thereof

A unique synthesis of a well-defined block copolymer having alternating maleic anhydride(MAn)/styrene(St) segments and PSt segments was achieved via radical addition–fragmentation chain transfer (RAFT) copolymerization and the self-assembly aggregating behavior of its hydrolyzed amphiphilic product in water was demonstrated.

Multiple morphologies of aggregates from block copolymers containing glycopolymer segments

Multiple morphologies of aggregates (micelle-like spheres, vesicles, tubules) from well-defined polystyrene-b-poly[(2-β-D-glucopyranosyloxy)ethyl acrylate] (PS-b-PGEA) diblock copolymers in diluted aqueous solutions were observed by transmission electron microscopy.

Synthesis and ring-opening polymerization of α-chloromethyl-α-methyl-β-propiolactone

α-Chloromethyl-α-methyl-β-propiolactone (CMMPL) was synthesized by dehydrohalogenation of α,α-dichloromethyl-β-propionic acid which was obtained by chlorination of α,α-hydroxymethyl-β-propionic acid (DMPA). Due to high strain of the four-numbered ring, CMMPL can be polymerized by ring-opening with or without an initiator. Both electrophiles like trifluoroacetic acid (TFAA) and nucleophiles like triethylamine (TEA) and pyridine, as well as organometallic compounds such as stannous octoate [Sn(Oct) 2 )], aluminium triisopropoxide [Al(O 1 Pr) 3 and tetrabutyl orthotitanate [Ti(OC 4 H 9 ) 4 ], were found to be effective initiators. The polymerization can be conducted by either solution or bulk polymerization. P(CMMPL) is insoluble in almost all organic solvents at room temperature. An endothermic peak (ca. 214 ∼ 250°C) attributed to the melting transition of P(CMMPL) was observed in DSC curves. P(CMMPL) tends to have high crystallinity (40% ∼ 60%) as demonstrated by its X-ray diffraction patterns, and the crystallinity was found to vary with the types of initiator used.

Vinyl monomers bearing chromophore moieties and their polymers. VIII. Synthesis and fluorescence behavior of a vinyloxy monomer having an electron-accepting chromophore moiety, p-((vinyloxy)methyl)benzonitrile and its polymers

A vinyloxy monomer having an electron-accepting chromophore moiety, p-((vinyloxy)methyl)benzonitrile (VOMBN), was synthesized by reaction of p-(hydroxymethyl)benzonitrile with ethyl vinyl ether (EVE) in the presence of mercuric acetate. VOMBN can easily be cationically homopolymerized and copolymerized with EVE by using Lewis acids such as boron trifluoride etherate (BF 3 . OEt 2 ) as a catalyst and radically copolymerized with maleic anhydride (MAn) using AIBN as an initiator. The fluorescence behaviors of VOMBN, its copolymer P(VOMBN-co-MAn), and its saturated model compound p-(ethoxymethyl)benzonitrile (EOMBN) were investigated in acetonitrile. It has been found that the fluorescence intensity ofVOMBN is much lower than its copolymer and EOMBN at the same chromophore concentration. A fluorescence structural self-quenching effect (SSQE) is also observed for VOMBN as we have reported previously [Li, F. M.; Chen, S. J.; Li, Z. C.; Qiu, J. J Polym Sci Polym Chem 1996, 34, 1881]. This phenomenon has been attributed to the inter- and intramolecular charge transfer interaction between the electron-accepting cyanophenyl chromophore and the electron-donating vinyloxy group in the same molecule. The dependence of the fluorescence intensity of VOMBN on solvents of different viscosities is evidence that the SSQE of VOMBN mainly occurs intramolecularly. The fluorescence of EOMBN and P(VOMBN-co-MAn) was quenched by a series of electron-rich vinyloxy compounds which do not have chromophore moieties, such as dihydrofuran (2H-furan), dihydropyran (2H-pyran), furan, and EVE. It is observed that the higher the electron-donating ability of the quenchers, the greater the quenching efficiency. P(VOMBN) and the random copolymers of VOMBN with EVE show broader fluorescence spectra as compared to the alternating copolymer P(VOMBN-co-MAn). This indicates that there is a mutual interaction between the adjacent cyanophenyl groups in P(VOMBN) and P(VOMBN-co-EVE), whereas such an interaction does not exist for P(VOMBN-co-MAn) in which the cyanophenyl groups are isolated by the rigid succinic anhydride rings.

Synthesis of hammer-like macromolecules of C60 with well-defined polystyrene chains via atom transfer radical polymerization (ATRP) using a C60-monoadduct initiator

A new preparation of uniform hammer-like macromolecules of C60 with designed molecular weight and narrow molecular weight distributions in the range of 1.13–1.37 is developed by using C60-monoadduct initiator (I) in a copper-mediated atom transfer radical polymerization (ATRP).

Vinyl monomers bearing chromophore moieties and their polymers. IV. Fluorescence and photosensitizing behavior of 8-acryloyloxyquinoline and its polymer

Acrylic monomers bearing electron-donating quinolyl moiety, i.e., 8-acryloyl-oxyquinoline (AQ) was prepared and polymerized. It was found that the fluorescence intensity of AQ was much lower than that of P(AQ) at the same chromophore concentration. The fluorescence of P(AQ) could be quenched by electron-deficient vinyl monomers, such as acrylonitrile (AN) and methyl methacrylate (MMA). This is another example of the fluorescence structural self-quenching effect termed by us previously, and demonstrates again that this phenomenon is not an accidental but a general one for acrylic monomers bearing electron-donating chromophores. The photopolymerization of acrylonitrile (AN) sensitized by AQ and P(AQ) as well as combining with carbon tetrabromide (CBr 4 ) was studied kinetically. From the rates of the polymerization (Rp) and overall activation energies obtained for these four systems, it was found that Rp sensitized by the binary systems was much higher than by AQ or P(AQ) alone, while the molecular weights of the resulting P(AN) were lower. The fluorescent analysis of the resulting P(AN)in solution showed that the sensitizers also entered into the P(AN) chains. A mechanism of charge transfer complex (CTC) formation was tentatively suggested for the photopolymerization of AN initiated by these four systems.

Ring‐opening copolymerization of α‐chloromethyl‐α‐methyl‐β‐propionolactone with ε‐caprolactone

α-Chloromethyl-α-methyl-β-propionolactone (CMMPL) has been copolymerized with e-caprolactone (CL) using a wide range of feed compositions and aluminium triisopropoxide [Al(OiPr)3] as an initiator. Random copolymers of CMMPL with CL were obtained. The pendant chloromethyl groups of the copolymer were converted to quaternary ammonium salts by reaction with pyridine, resulting in an increased hydrophilicity of the copolymers.