Resulting Block Copolymers Research Articles

Preparation of ABCBA‐type block copolymers by use of macro‐initiators containing peroxy and azo groups

AbstractSome new macroinitiators (5) containing azo and peroxy groups were synthesized by transformation of esters of poly(ethylene glycol) (1) (PEG) of different molecular weight with hydroxyl end groups and an azo group in the middle into the corresponding polymers with tert‐butylperoxycarbonyl end groups by reaction with terephthaloyl chloride and subsequently with tert‐butyl hydroporoxide. Decomposition in the presence of styrene at 60°C or with 3,6,9‐triazaun‐decane‐1,11‐diamine in presence of methyl methacrylate gave the corresponding ABA block copolymer 6 and the ABBA block copolymer 7, respectively. Both block copolymers were used as polymeric initiators. The ABCBA block copolymer 8 was synthesized from 6 and methyl methacrylate or from 7 and styrene by thermally induced polymerization at 80°C. The resulting block copolymers were separated from the homopolymers by selective solvent extraction and characterized by spectroscopic and fractional precipitation methods.

Long-lived polymer radicals

When N-acryloyl-L-valine(ALV) was photo-polymerized in ethyl acetate, the resulting polymerization mixture was found to contain the living propagating radical of ALV. Synthesis of block copolymers was attempted by using the reaction of living poly(ALV) radical with some vinyl monomers. The resulting block copolymers were characterized by IR spectroscopy, dynamic thermogravimetry and pyrolysis gas chromatography.

Preparation of a Novel Block Copolymer by the Anionic Polymerization of a Bicyclic Oxalactam Activated with Isocyanate-Terminated Polyoxyethylene and Characterization of Its Hydrophilic Membrane

A new block copolymer composed of polyamide as outer segments and polyoxyethylene as an inner segment was prepared by the anionic polymerization of a bicyclic oxalactam, 8-oxa-6-azabicyclo[3.2.1]octan-7-one. A polyoxyethylene having terminal isocyanate groups was used as an activator obtained from polyoxyethylene glycol and an excess of tolylene-2,4-diisocyanate. A hydrophilic membrane was easily obtained by casting from a chloroform–methanol (10: 1) solution of the resulting block copolymer. The interaction of the copolymer membrane with water molecules was discussed in relation to the adsorption and permeation of water.

Metal-Containing initiator Systems. XXXVI. Synthesis of Block Copolymer of Methyl Acrylate and α-Methylbenzyl Methacrylate with Binary Initiator System of Cobaltocene and Bis(ethyl acetoacetato)copper(II)

Abstract Polymerizations of methyl acrylate (MA) and (DL)-α-methyl-benzyl methacrylate (MBMA) with binary initiator system of cobaltocene [Co(C5H5)2] and bis(ethyl acetoacetato)copper(II) [Cu(eacac)2] were studied in acetonitrile at 25°C. The molecular weight of the polymers obtained by MA was found to increase with time in the early stage of polymerization. Although MBMA was also polymerized by this system, asymmetric selective polymerization was not induced in the presence of (-)-sparteine. The synthesis of the block copolymer of MA and MBMA was attempted by using this initiator system. The block copolymer was obtained in 90% yield in the polymerization of MBMA with a polymer radical which prepared from MA with this system for 1 day. The yield of the block copolymer depended on the prepolymeriza-tion time of MA by this system. The resulting block copolymer was characterized by IR, 1H-NMR, and gel-permeation chromatography.

Metal‐containing initiator systems, 35. Synthesis of block copolymers by using the binary initiator system cobaltocene/bis(ethyl acetoacetato)copper(II)

AbstractPolymerization of methyl methacrylate (MMA) with the binary initiator system cobalt‐ocene (Co(C5H5)2)/bis(ethyl acetoacetato)copper(II)(Cu(eacac)2), was studied kinetically at 25°C in acetonitrile. The relationship between yield and molecular weight of the resulting poly(MMA) was suggestive of a living polymerization character in this system. The synthesis of block copolymers of MMA with styrene (St) was attempted by adding St as the second monomer to the polymerization system of MMA. The block copolymer was formed in a yield of 20% when MMA was polymerized for 1 day, while the yield went up to 80% when the MMA polymerization was carried out for 3 days. The resulting block copolymer was characterized by IR spectroscopy and gel‐permeation chromatography.

Long‐lived polymer radicals. III. Synthesis of block copolymer by the reaction of living poly(N‐methylacrylamide) radical with some vinyl monomers

AbstractN‐Methylacrylamide (NMAAm) was polymerized quantitatively by using di‐tert‐butyl peroxide as photosensitizer to be, for the most part, incorporated in living poly(NMAAm) radical. The living polymer radical reacted effectively with acrylate monomers to yield block copolymer. Longer alkyl chain of the acrylate monomer caused a decrease in the conversion of the second monomer. Methacrylate monomers, such as methyl methacrylate and cyclohexyl methacrylate, showed relatively low reactivities in comparison with acrylates. Styrene exhibited a much lower conversion. The resulting block copolymers showed different thermochromic behaviors in methyl benzoate from that of poly(NMAAm). This is explained on the basis of the difference between refractive indexes of the block copolymers and poly(NMAAm).

Synthesis and Characterization of Triblock Copolymer of Poly(tetramethylene Oxide) and Poly(methyl Methacrylate)

Abstract Anionic polymerization of methyl methacrylate (MMA) was initiated with the disodium salt of dihydroxy-poly(tetra-methylene oxide) (PTMO) in tetrahydrofuran in the presence and the absence of a crown ether. The resulting block copolymer of poly(methyl methacrylate) (PMMA) and PTMO was characterized by 1H NMR spectroscopy, gel permeation chromatography, and solvent extractions. In the absence of the crown ether, a linear triblock copolymer of PMMA-PTMO-PMMA was predominantly obtained, showing a unimodal and relatively narrow molecular weight distribution. In the presence of the crown ether, a linear triblock copolymer and a PTMO grafted block copolymer due to the transesterification reaction between PTMO and a methoxy group in MMA were produced with an increase in polymer yield. The stereosequence distributions of the PMMA part in the copolymers were essentially atactic and the addition of the crown ether increased the fraction of the rr triad. A-B-A type triblock copolymers have recently received much attention because they contain physically and chemically incompatible segments in one macromolecular chain. A large number of block copolymers have been synthesized by various techniques [1]. Due to the low melting and glass transition temperatures of poly(tetramethylene oxide) (PTMO), it is suitable for the center block. Several attempts have been made to synthesize block copolymers of PTMO and a few monomers [2–10]. Tobolsky and his co-workers prepared a peroxide-terminated PTMO and tried to initiate the radical polymerization of methyl methacrylate (MMA) [5]. However, appreciable amounts of MMA homopolymer and unreacted PTMO existed in the product in addition to the block copolymer of PTMO and poly(methyl methacrylate) (PMMA). They could not isolate the pure block copolymer and could not characterize the resulting copolymer. In previous papers we have studied syntheses of the A-B-A type triblock copolymers of poly(ethylene oxide) (PEO) and PMMA [11, 12] and of PEO and polymethacrylonitrile [13] by using the disodium salt of PEO as an initiator. As an extension of this technique, we have investigated the capability of initiating the polymerization of MMA with the disodium salt of PTMO, which is considered to be inferior to PEO in cation-binding ability. The present paper describes the synthesis and characterization of a triblock copolymer of PTMO and PMMA. The effect of the addition of a crown ether on the polymerization is discussed.

Synthesis and Characterization of Block Copolymers of Poly(ethylene oxide) and Poly(methyl methacrylate)

Anionic polymerization of methyl methacrylate (MMA) was initiated with the disodium salt of poly(ethylene oxide) (PEO) in tetrahydrofuran (THF) in both the presence and absence of a crown ether or cryptate. The resulting block copolymer of poly(methyl methacrylate) (PMMA) and PEO was characterized by 1H- and 13C-NMR spectroscopies, gel-permeation chromatography and solvent extractions. The transesterification reaction between PEO and methoxy group in MMA was accompanied by polymerization, resulting in a PEO grafted triblock copolymer. A benzylamino derivative of PEO (PEO–N) was prepared as a new initiator system for the polymerization of MMA. The initiation with disodium or dilithium amide of PEO–N resulted in a linear triblock copolymer of PMMA–PEO–PMMA having a unimodal and narrower molecular weight distribution. The stereosequence distributions of the PMMA part in the copolymers were essentially atactic and the addition of the crown ether or the cryptate increased the fraction of the rr triad.

D2‐m‐carboranesiloxanes. VIII. Preparation and characterization of carboranesiloxane/polysulfone alternating block copolymer

AbstractA D2‐m‐dodecacarboranesiloxane containing alternating block copolymer \documentclass{article}\pagestyle{empty}\begin{document}$\rlap{--}[{\rm A}\hbox{---}{\rm B}\rlap{--}]_n$\end{document} was prepared by the reaction of a ureidosilane‐terminated polysulfone hard block with a carboranesilanol‐terminated carboranesiloxane oligomer. The resulting block copolymer exhibited thermoplastic elastomeric behavior. This unique polymer had excellent thermal stability up to 400°C.