Poly block copolymers structure

Hoogenboom R, Schubert US, van Camp W et al. (2005) RAFT polymerization of 1-ethoxy ethyl acrylate a novel route toward near-monodisperse poly(acrylic add) and derived block copolymer structures. Macromolecules 38 7653-7659... 

The living nature of the poly(styryl)anion allows one to prepare block copolymers with a great deal of control of the block copolymer structure. The preparation of diblock, triblock, and other types of multiblock copolymers has been reviewed [29-32]. Several of these block copolymers are in commercial use. The basic concept involves first preparing polystyrene block [RSt StLi—see Eq. (2)] and then adding a new monomer that can be added to start another growing segment. 

The use of polysilanes as photoinitiators of radical polymerization was one of the hrst means whereby they were incorporated within block copolymer structures [38 0], albeit in an uncontrolled fashion. However the resulting block copolymer structures were poorly defined and interest in them principally lay in their application as compatibilisers for polystyrene (PS) and polymethylphenylsilane blends PMPS. The earliest synthetic strategies for relatively well-defined copolymers based on polysilanes exploited the condensation of the chain ends of polysilanes prepared by Wurtz-type syntheses with those of a second prepolymer that was to constitute the other component block. Typically, a mixture of AB and ABA block copolymers in which the A block was polystyrene (PS) and the B block was polymethylphenylsilane (PMPS) was prepared by reaction of anionically active chains ends of polystyrene (e.g. polystyryl lithium) with Si-X (X=Br, Cl) chain ends of a,co-dihalo-polymethylphenylsilane an example of which is shown in Fig. 2 [43,44,45]. Similar strategies were subsequently used to prepare an AB/ABA copolymer mixture in which the A block was poly(methyl methacrylate) (PMMA) [46] and also a multi- block copolymer of PMPS and polyisoprene (PI) [47]. 

The first commercial thermoplastic elastomers deriving their properties from an ABA block copolymer structure were poly(styrene-isoprene-styrene) and poly (styrene-butadiene-styrene) triblocks introduced in 1965 at an ACS Rubber... 

Anionic polymerizations are particularly useful for synthesizing block copolymers. These macromolecules contain long sequences of homopolymers Joined together by covalent bonds. The simplest vinyl-type block copolymer is a two segment molecule illustrated by structure (9-2). This species is called an AB block copolymer, because it is composed of a poly-A block joined to a long sequence of B units. Other common block copolymer structures are shown as (9-3)-(9-6). 

The most important polyether, PO-EO block copolymer structures, having terminal poly[EO] block (structure a) and internal poly[EO] block (structures b and c), are presented in Figure 4.28. 

Liquid crystal block copolymers are a recently explored group of polymers which combine microphase separation and liquid crystallinity. Yet, as early as 1963, Gratzer and Doty [37] reported the first block copolymers containing two polypeptide blocks in which one of the blocks, poly(y-benzyl-L-glutamate) (PBLG), was already well known to be liquid crystalline. In principle, all the LCP structures shown in Fig. 1 can be incorporated into block copolymer structures with a second flexible coil or LC block. Some of the possible LC-BCP structures are shown in Fig. 2. Due to the limited nature of this review, structures such as the grafted LC copolymers [38] and various multiblock LC copolymers [39] will not be covered. 

Martinelli, E. Galli, G. Krishnan, S. Paik, M. Y. Ober, C. K. Fischer, D. A., New Poly (dimethylsiloxane)/Poly(perflurooctyl acrylate) Block Copolymers Structure and Order Across Multiple Length Scales in Thin films. J. Mater. Chem. 2011,21,15357-15368. 

Liquid crystal polymers are becoming of increasing interest. The preparation of a polyester-amide by acidolysis of poly(ethylene terephthalate) with p-acetamido-benzoic acid followed by polycondensation through the acetamido and carboxyl groups gives a polymer with liquid crystal properties. In contrast a series of polyester amides with block copolymer structures had elastoplastic characteristics. ... 

In Table 7.1 are schematically indicated several typical block copolymer structures which can be obtained by combining poly A and poly B sequences. 

Optical rotation (OR) readings increased with polymerization time and eventually leveled off. GPC measurement showed approximately 50 mol.% consumption of rac-LA. In the second step, an equimolar quantity of (R)-SB(OH)2 (with respect to the S enantiomer) was introduced. In subsequent polymerization, a gradual decrease in OR was observed. Taking into account the determined stereoelectivity coefficient. Pm = 0.96, for the final poly(rac-LA), the gradient poly[(S,S)-lA-grad- R,R)-lA] rather than the block copolymer structure was expected. Indeed, homodecoupled NMR spectra showed, apart from the strong signal of the isotactic mmm... 

Ethylene oxide/styrene block copolymers have been further free-radical copolymerized with other ethylenically unsaturated compounds such as methyl methacrylate and methacrylic acid in benzene, tetrahydrofuran, and dimethylformamide (176). Correlations were made between reactivity ratio and solvent dielectric constant, as well as between solubility parameters of reaction solvent and growing polymer chains with marked effects apparent. Gel permeation chromatography of diblock and triblock copolymers based on polystyrene and poly(ethylene oxide) has revealed interesting molecular characteristics (177). Such block copolymers have an amphiphilic character. In aqueous solution, the polymers form spherical micells with a polystyrene core and a poly(ethylene oxide) outer sheath. The investigations used an aqueous-methanolic solution and were able to ascertain block copolymer structures and to estimate the impurities in the diblock copolymer. 

For well-controlled arm number of the star polymers, an efficient approach is the use of multifunctional initiators [157,158]. For instance, the four-armed initiator, NLI-1, which was prepared by the condensation reaction of the hydroxy groups in C(CH20CH2CH2CH20H)4 with a-bromoisobutyric acid, was used in the ATRP of (2,2-dimethyl-l,3-dioxoIane-4-yl)methyl acrylate (DMDMA) with CuBr/bpy as catalyst. After isolation from the polymerization system, four-armed poly(DMDMA)s, such as NLI-2 with Mw/Mn = 1.28—1.41 were obtained, and used in the successive ATRP of MMA, giving star-block copolymers NLB-3. It is known that the cycloacetal ring is unstable in acidic conditions, so the hydrolysis of the block copolymer NLB-3 was accomplished in a 1N HCl aqueous solution to give the amphiphilic star-block copolymer structure NLB-4 as shown in Scheme 3.37 [159]. 

Another important type of condensation polymer are the linear polyesters, such as poly (ethylene terephthalate) (PET) and poly (butylene terephthalate) (PBT). Copolymers of polyesters and PA have been studied in detail, and it has been shown that random copolyesteramides have a low structural order and a low melting temperature. This is even the case for structurally similar systems such as when the group between the ester unit is the same as that between the amide unit, as in caprolactam-caprolactone copolymers (Fig. 3.10).22 Esters and amide units have different cell structures and the structures are not therefore isomorphous. If block copolymers are formed of ester and amide segments, then two melting temperatures are present. 

See also PBT degradation structure and properties of, 44-46 synthesis of, 106, 191 Polycaprolactam (PCA), 530, 541 Poly(e-caprolactone) (CAPA, PCL), 28, 42, 86. See also PCL degradation OH-terminated, 98-99 Polycaprolactones, 213 Poly(carbo[dimethyl]silane)s, 450, 451 Polycarbonate glycols, 207 Polycarbonate-polysulfone block copolymer, 360 Polycarbonates, 213 chemical structure of, 5 Polycarbosilanes, 450-456 Poly(chlorocarbosilanes), 454 Polycondensations, 57, 100 Poly(l,4-cyclohexylenedimethylene terephthalate) (PCT), 25 Polydimethyl siloxanes, 4 Poly(dioxanone) (PDO), 27 Poly (4,4 -dipheny lpheny lpho sphine oxide) (PAPO), 347 Polydispersity, 57 Polydispersity index, 444 Poly(D-lactic acid) (PDLA), 41 Poly(DL-lactic acid) (PDLLA), 42 Polyester amides, 18 Polyester-based networks, 58-60 Polyester carbonates, 18 Polyester-ether block copolymers, 20 Polyester-ethers, 26... 

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