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Block Copolymer Synthesis - Springer

Several examples of block copolymer template-directed synthesis of continuous metallic nanostructures will be described and the prospects of this approach will be discussed.

The illustration of synthetic route of carboxylated triblock copolymer F127 (F127COOH).

To investigate the biodistribution of FA conjugated micelle encapsulated QDs in the tumor-bearing mice, the mice were sacrificed and major organs and tumor were removed for luminescence imaging after intravenously injected with 4 mg of QDs bioconjugates for 3 to 4 h. Figure shows luminescent images of heart, liver, spleen, lung, and kidney obtained from a mouse after injection of FA-QD formulation. As observed from the characteristic red-emitting color of QDs, the QDs are mainly accumulated in the tumor, with some QDs accumulation in the liver, spleen, and kidney. No accumulation of QDs was observed in the heart and lung. Previously, Gao et al. reported the use of functional CdSe/ZnS QDs for in vivo tumor imaging by incorporating QDs into the core of block copolymer nanoparticles []. They have reported a similar trend of QD biodistribution in the organs.

Block copolymer synthesis - ScienceDirect

The synthesis of block copolymers (An-b-Tn) was carried out analogously to methods developed previously in our laboratory [,]. For example the synthesis of BCP-A50T50 was performed by sequential addition of monomers. Monomer A 7 (15 mg, 0.071 mmol) dissolved in 1 ml of CH2Cl2 was introduced into a heated and argon flushed glass tube equipped with a magnetic stirring bar. To this solution, catalyst G3 (1.26 mg, 0.0014 mmol) dissolved in 1 ml of CH2Cl2 was then added. The mixture was allowed to stir at room temperature for 1 h until all of the monomer A 7 was consumed as confirmed by GPC and TLC. Subsequently, monomer T 9 (35 mg, 0.071 mmol) dissolved in 1 ml of CH2Cl2 was then added to the above reaction mixture and stirred for 2 h at room temperature until all of monomer T 9 was consumed, as confirmed by GPC and TLC. The polymerization was quenched by the addition of cold ethyl vinyl ether. The polymer was isolated by column chromatography (SiO2) (eluent: DCM).

The synthesis of new block copolymers containing free radical centers within one block via ROMP has been described. MALDI analyses especially provide a detailed picture of the crossover reaction. Basically, the NEOLYST catalysts are comparable to the well known Grubbs’ catalysts, indicating a similar profile of initiation and propagation. However, the catalyst U3 is especially a highly potent catalyst for ROMP and displays a broad profile of tolerance against functional groups within the monomer, enabling the successful synthesis of block copolymers containing free-radical species in high densities.

One kind of copolymer is called a "block copolymer".

The respective MALDI spectrum of the crossover reaction of the homopolymer A25 with exactly two equivalents of monomer T 9 is shown in . Again, a significant amount of homopolymer An (visible as AnNa+-series) is present in the reaction mixture, the respective crossover-species AnT1, and AnT2 can be seen as the respective Na+-ions. Additionally, the respective series AnT3 is visible, indicative of the further chain growth process after the crossover reaction. Again, despite the excess of Tn-species a large amount of An-species did not participate in the crossover reaction due to the fast polymerization of monomer T 9. MALDI spectra of a further series of block copolymers A25T5 and A25T25 was carried out in order to check for the presence of residual homopolymer A25 in the polymer mixture (see ). We could not detect any residual homopolymer in either of these final samples. As it is known from our previous investigations, that the homopolymer An in MALDI is desorbed preferentially by a factor of 13 with respect to the A25Tn-species, this now indicates a complete cross-over reaction and thus the successful preparation of block copolymers AnTm via this methodology. Basically, this synthetic approach now allows the synthesis of AT type BCP’s with high precision and chain length control up to molecular weights of ~31000 g/mol.

For the structure of micelle-encapsulated QDs, QDs are coated in sequence of coordinating ligands, such as hydrophobic surfactants (TOPO and oleic acid), the hydrophobic section of triblock polymer (PPO-(PEO)n-COOH) and hydrophilic section of triblock polymer (PPO-(PEO)n-COOH). The oil-like layer between TOPO/oleic acid with PPO formed a lamellar layer to protect the inner QDs. Meanwhile, the carboxyl group on the PEO surface plays an important role for QDs to maintain the colloidal stability, as well as to provide site for the biomolecule conjugation with the purpose of cell targeting. The micelle-encapsulated QD samples, with or without FA conjugation, can remain well-suspended in aqueous dispersion under pH 7.4, with no aggregation for more than six months at ambient temperature and no loss of any photoluminescence intensity.

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Block Copolymer Synthesis: NMP Approach | Sigma-Aldrich

AB - Block copolymerization of ethylene with 5-norbornen-2-yl acetate (1) by the nickel catalyst system [N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)propanamide]Ni(η1-CH2Ph)(PMe3) (2) and Ni(COD)2 (bis(1,4-cyclooctadiene)nickel) (3) produces a variety of block copolymer structures that demonstrate microphase separation. Typical block copolymerizations were carried out in an autoclave charged with a solution of the catalyst mixture and 1 (0.15 M) in toluene. The autoclave was sealed and exposed to PC2H4 = 50 psi for a period of time (T1). A pressure jump to PC2H4 = 1100 psi was then applied and the reaction allowed to proceed for another predetermined interval (T2). Independent experiments were performed to isolate and examine the molecular weight and comonomer composition of the first block. Narrow molecular weight distributions and the increase of polymer molecular weight with increases in T1 or T2 are consistent with a product in which an initial block is formed at low ethylene pressures and quantitatively converted to a block copolymer by the jump to high pressure. Transmission electron microscopy confirms that the materials are microphase separated.

Synthesis of Styrene−Acrylonitrile Copolymers and …

N2 - Block copolymerization of ethylene with 5-norbornen-2-yl acetate (1) by the nickel catalyst system [N-(2,6-diisopropylphenyl)-2-(2,6-diisopropylphenylimino)propanamide]Ni(η1-CH2Ph)(PMe3) (2) and Ni(COD)2 (bis(1,4-cyclooctadiene)nickel) (3) produces a variety of block copolymer structures that demonstrate microphase separation. Typical block copolymerizations were carried out in an autoclave charged with a solution of the catalyst mixture and 1 (0.15 M) in toluene. The autoclave was sealed and exposed to PC2H4 = 50 psi for a period of time (T1). A pressure jump to PC2H4 = 1100 psi was then applied and the reaction allowed to proceed for another predetermined interval (T2). Independent experiments were performed to isolate and examine the molecular weight and comonomer composition of the first block. Narrow molecular weight distributions and the increase of polymer molecular weight with increases in T1 or T2 are consistent with a product in which an initial block is formed at low ethylene pressures and quantitatively converted to a block copolymer by the jump to high pressure. Transmission electron microscopy confirms that the materials are microphase separated.

Block Copolymers: Synthetic Strategies, Physical Properties, ..

The polymerization of monomer 7 was investigated using catalysts U1U3 (see ). Basically, the catalyst U3 showed good polymerization behavior, furnishing the homopolymers (entries 2, 3) with excellent control of chain length and low polydispersities (Mw/Mn = 1.2). The catalysts U1 and U2 gave poor results (see entries 4 and 5) presumably due to slow initiation and fast polymerization, which is in accord with the structurally similar catalysts G1 and G2 (see ). Similarly, the polymerization of monomer T 9 was investigated, which gave good results with the catalysts G2, G3, and U3 (entries 6, 7, and 8). The other catalysts G1, U1, and U2 did not yield good polymerization results (data not shown) and were therefore not considered further for the synthesis of the respective block copolymers.

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