T block copolymers

Figure 9 Changes of relative transmittance decreasing with pH values of the solution. PLLA/PEG ( ), PLLA/PEG-SD (o), and PLLA/PEG-PSD (T) block copolymer. (Adapted from Ref. 90.)...

Kwon GS, Naito M, Kataoka K, Yokoyama M, Sakurai Y, Okano T. Block copolymer micelles as vehicles for hydrophobic drugs. Colloid Surf B 1994 2 429-434. 

Waldman D A, Kolb B U, McCarthy T J and Hsu S L 1988 Infrared study of adsorbed monolayers of poly(styrene-propylene sulphide) (PS-PPS) block copolymers Polym. Mater. Sc/. Eng. 59 326-33... 

Noncrystalline aromatic polycarbonates (qv) and polyesters (polyarylates) and alloys of polycarbonate with other thermoplastics are considered elsewhere, as are aHphatic polyesters derived from natural or biological sources such as poly(3-hydroxybutyrate), poly(glycoHde), or poly(lactide) these, too, are separately covered (see Polymers, environmentally degradable Sutures). Thermoplastic elastomers derived from poly(ester—ether) block copolymers such as PBT/PTMEG-T [82662-36-0] and known by commercial names such as Hytrel and Riteflex are included here in the section on poly(butylene terephthalate). Specific polymers are dealt with largely in order of volume, which puts PET first by virtue of its enormous market volume in bottie resin. 

Similarly, the random introduction by copolymerization of stericaHy incompatible repeating unit B into chains of crystalline A reduces the crystalline melting point and degree of crystallinity. If is reduced to T, crystals cannot form. Isotactic polypropylene and linear polyethylene homopolymers are each highly crystalline plastics. However, a random 65% ethylene—35% propylene copolymer of the two, poly(ethylene- (9-prop5lene) is a completely amorphous ethylene—propylene mbber (EPR). On the other hand, block copolymers of the two, poly(ethylene- -prop5iene) of the same overall composition, are highly crystalline. X-ray studies of these materials reveal both the polyethylene lattice and the isotactic polypropylene lattice, as the different blocks crystallize in thek own lattices. 

Whereas random copolymers exhibit one T described by equation 38, block copolymers, because of this microphase separation, exhibit two glass-transition temperatures. The T of each block is close to, if not the same as, the homopolymer from which it was formed. Polymer properties are also affected by the arrangement of the blocks. This is shown for high styrene-containing or high molecular-weight styrene resias of various block arrangements ia Table 3. 

The second front originates in the polymer synthesis community. Efforts are mainly directed toward production of monodisperse block copolymers by living polymerizations. These stmctures typically result in microphase separated systems if one block is a high T material and the other is elastomeric in... 

Global consumption of thermoplastic mbbers of all types is estimated at about 600,000 t/yr (51). Of this, 42% was estimated to be consumed in the United States, 39% in Western Europe, and 19% in Japan. At present, the woddwide market is estimated to be divided as follows styrenic block copolymers, 48% hard polymer/elastomer combinations, 26% thermoplastic polyurethanes, 12% thermoplastic polyesters, 4% and others, 9%. The three largest end uses were transportation, 23% footwear, 18% and adhesives, coatings, etc, 16%. The ranges of the hardness values, prices, and specific gravities of commercially available materials are given in Table 4. 

Most types of PSAs have found some application in the label industry. Block copolymer-based adhesives are perhaps the most popular because of their high adhesion to a variety of surfaces, their low cost, their good performance over a range of temperatures and peel rates, and their ease of processing. For applications where high temperature performance is required, block copolymers have been formulated with high T end block associating resins or polymers. 

F. S. Bates, W. Maurer, T. Lodge, M. F. Schulz, M. W. Matsen, K. Almdal, K. Mortensen. Isotropic Lifshitz behavior in block copolymer-homopolymer blends. Phys Rev Lett 75 4429-4432, 1995. 

S-B-S Triblocks are block copolymers consisting of a block of butadiene units flanked by blocks of styrene. Below the T, of polystyrene blocks from different chains congregate into domains which act both as cross-links and reinforcing fillers. The jDolymers will dissolve in hydrocarbon solvents. Hydrogenated S-B-S materials have better resistance to ageing. 

Sato, T. and Otsu, T. Formation of Living Propagating Radicals in Microspheres and Their Use in the Synthesis of Block Copolymers. Vol. 71, pp. 41 —78. 

Sakurai S., Kawada H., Hashimoto T., and Fetters L.J. Thermoreversible morphology transition between spherical and cyUndrical microdomains of block copolymers. Macromolecules, 26, 5796, 1993. 

Hasegawa H., Hashimoto T., Kawai H., Lodge T.P., Amis E.J., Glinka C.J., and Han C. SANS and SAXS studies on molecular conformation of a block copolymer in microdomain space. 2. Contrast matching technique. Macromolecules, 18, 67, 1985. 

Tanaka H. and Nishi T., Study of block copolymer interface by pulsed NMR, J. Chem. Phys., 82, 4326, 1985. 

Hashimoto T., Shibayama M., and Kawai H., Ordered structure in block copolymer solution. 4. Scaling rules on size of fluctuations with block molecular weight, concentration temperature in segregation and homogeneous regimes. Macromolecules, 16, 1093, 1983. 

Hashimoto T., Order disorder transition in block copolymers. Thermoplastic Elastomers A Comprehensive Review (Legge N.R., Holden G., and Schroeder H.E., eds.), Hanser Publishers, Munich, 1987. Bianchi U. and Pedemonte E., Morphology of styrene butadiene styrene copolymer. Polymer, 11, 268, 1970. 

Cakmak M. and Wang M.D., Structure development in the tubular blown film of PP/EPDM thermoplastic elastomer, Antec 89, 47th Annual Tech. Conference of SPE, New York, May 1, 1989, 1756. Hashimoto T., Todo A., Itoi H., and Kawai H. Domain boundary structure of styrene-isoprene block copolymer films cast from solution. 2. Quantitative estimation of the interfacial thickness of lamellar microphase systems. Macromolecules, 10, 377, 1977. 

Inoue T., Soen T., Hashimoto T., and Kawai, H. Studies on domain formation of the A-B t3fpe block copolymer with polystyrene and polyisoprene. Macromolecules, 13, 87, 1970. 

Kirkpatrick J.P. and Preston D.T., Polymer modification with styrenic block copolymers, Elastomerics, 120, 30, 1988. 

Jeoung E., Galow T.H., Schotter J., Bal M., Ursache A., Tuominen M.T., Stafford C.M., Russell T.P., and Rotello V.M. Fabrication and characterization of naoelectrode arrays formes via block copolymers self-assembly, Langmuir, 17, 6396, 2001. 

Hashimoto T., Tsutsumi K., and Funaki Y., Nanoprocessing based on bicontinuous microdomains of block copolymers Nanochannel coated with metals, Langmuir, 13, 6869, 1997. 

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