Thermotropic Liquid Crystalline Polymers
Michael Jaffe, Si-Xue Cheng,
Tai-Shung Chung, Yakov Freidzon, Anthony J. East,
Si-Xue Cheng
Department of Chemistry, Wuhan University, Wuhan, People's Republic of China
Search for more papers by this authorAnthony J. East
Department of Central Research, Hoechst Celanese, Chatham, NJ, USA
Search for more papers by this authorMichael Jaffe, Si-Xue Cheng,
Tai-Shung Chung, Yakov Freidzon, Anthony J. East,
Si-Xue Cheng
Department of Chemistry, Wuhan University, Wuhan, People's Republic of China
Search for more papers by this authorAnthony J. East
Department of Central Research, Hoechst Celanese, Chatham, NJ, USA
Search for more papers by this authorAbstract
Herein we present recent studies on the nature of thermotropic liquid crystalline polymers (LCPs) and their progress. Side-chain liquid crystals are also discussed briefly, showing the similarities and differences between these closely related molecules. We summarize and review the newly developed thin-film polymerization technique for the investigation of liquid crystalline formation as a function of monomer moieties, and for the study of reaction kinetics, evolution of liquid crystal texture, and surface energy during polycondensation reactions. We also highlight various modification approaches to yield main-chain LCPs suitable for conventional processing equipment, without compromising the unique liquid crystalline characteristics and superior mechanical properties. The thermal stability, degradation behavior, and crystallization kinetics of commercially available main-chain LCPs are recapitulated. Attention is also given to the rheology, polymer blends, micro- and nanostructures, processing of LCPs, and their applications. In the past decade, investigations of thermotropic LCPs have decreased from the high interest and publication rate of the latter part of the twentieth century. However, the number of monomer combinations giving rise to main-chain thermotropic polymers has increased and the origin of LCP rheology and morphology have been elucidated. The most important new work is the invention and description of thermotropic thermosets.
Bibliography
- 1 H. Baumgärtel, E. U. Franck, W. Grünbein, and H. Stegemeyer, eds., Topics in Physical Chemistry, Liquid Crystals, Springer, New York, 1994, Vol. 3.
- 2 G. W. Gray and P. A. Winsor, eds., Liquid Crystals & Plastics Crystals, John Wiley & Sons, Inc. New York, 1974, Vol. 1.
- 3 A. A. Collyer, Liquid Crystal Polymers: From Structures to Applications, Elsevier Applied Science, London, 1992.
- 4 E. Chiellini, M. Giordano, and D. Leporini, eds., Structure and Transport Properties in Organized Polymeric Materials, World Scientific, Singapore, 1997.
- 5 T. S. Chung, G. W. Calundann, and A. J. East, Encyclopedia of Engineering Materials, Marcel Dekker, Inc., New York, 1989, Vol. 2, p. 625.
- 6 P. J. Flory, Proc. R. Soc. London, ser. A 243, 73 (1956).
- 7 P. J. Flory, in Recent Advances in LCPs, Elsevier Applied Science, London, 1985.
- 8(a) U.S. Pat. 3575933 (1971), E. F. Hoegger, J. R. Schaefgen, and C. W. Stephens; (b) U.S. Pats. 3600350 (1971) and3671542 (1972), S. L. Lwolek; (c) U.S. Pat. 3943110 (1976), P. W. Morgan (to E. I. du Pont de Nemours & Co., Inc.).
- 9 M. Jaffe, Encyclopedia of Polymer Science and Engineering, John Wiley & Sons, Inc., New York, 1987, Vol. 7, p. 699.
- 10(a) U.S. Pat. 3637595 (1972), G. Cottis, J. Economy, and B. E. Nowak; (b) U.S. Pat. 3759870 (1973), J. Economy and B. E. Nowak (to Carborundum).
- 11 J. Economy and co-workers, J. Polym. Sci., Polym. Chem. 14, 2207 (1976).
- 12(a) U.S. Pats. 3778410 (1973) and 3804805 (1974), H. F. Kuhfuss and W. J. Jackson Jr.; (b) U.S. Pats. 4153779 (1979), W. J. Jackson, G. G. Gebeau, and H. F. Kuhfuss, (to Eastman Kodak).
- 13 W. J. Jackson, Brit. Polym. J. 12, 153 (1980).
- 14 W. J. Jackson, Mole. Cryst. Liq. Cryst. 169, 23 (1989).
- 15(a) U.S. Pat. 4067852 (1978), 4161470 (1979), 4184996 (1980), G. W. Calundann; (b) U.S. Pat. 4330457 (1982), A. J. East, L. F. Charbonneau, and G. W. Calundann (to Ticona).
- 16 G. W. Calundann and M. Jaffe, in Proceedings of the Robert A. Welch Conferences on Chemical Research, Vol. XXVI, Synthetic Polymers, (1982), p. 247.
- 17 T. S. Chung, Advances in Thermotropic LCPs, Technomic, Lancaster, Pa., 2001.
- 18 T. S. Chung, Polymer Engineering and Science 26, 901 (1986).
- 19 A. A. Collyer, Mater. Sci. Technol. 5, 309 (1989).
- 20 J. Economy and K. Goranov, Adv. Polym. Sci. 117, 221 (1994).
- 21 J. I. Jin JI and C. S. Kang, Prog. Polym. Sci. 22, 937 (1997).
- 22 H. Han and P. K. Bhowmik, Prog. Polym. Sci. 22, 1431 (1997).
- 23 A. M. Donald and A. H. Windle, LCPs, Cambridge University Press, Cambridge, UK, 1992.
- 24
V. P. Shibaev and L. Lam, eds., LC and Mesomorphic Polymers, Springer-Verlag, New York, 1994.
10.1007/978-1-4613-8333-8 Google Scholar
- 25 A. Ciferri, ed., Liquid Crystallinity in Polymers: Principles and Fundamental Properties, VCH Publishers, New York, 1991.
- 26 R. A. Weiss and C. K. Ober, LCPs, American Chemical Society, Washington, D.C., 1990.
- 27
S. Onogi and T. Asada, in G. Astarita, G. Marrucci, and L. Nicolais, eds., Rheology, Plenum Press, New York, 1980.
10.1007/978-1-4684-3740-9_9 Google Scholar
- 28 K. F. Wissbrun, Journal of Rheology 25, 619 (1981).
- 29 R. E. Jerman and D. G. Baird, Journal of Rheology 25, 272 (1981).
- 30 F. N. Cogswell and K. F. Wissbrun, in D. Acierno and A. A. Collyer, eds., Rheology and Processing of LCPs, Chapman & Hall, New York, 1996, Chapt. 4.
- 31 D. E. Turek and G. P. Simon, Polymer 34, 2750 (1993).
- 32 A. Datta and D. G. Baird, Polymer 36, 505 (1995).
- 33 M. T. De Meuse and M. Jaffe, Mol. Cryst. Liq. Cryst. 157, 535 (1988).
- 34 M. Jaffe, P. Chen, E. W. Choe, T. S. Chung, and S. Makhija, in P. Hergenroth eds., Advances in Polymer Science, Vol. 117, Springer Verlag, New York, 1994, p. 297.
- 35 Kamal and co-workers, Liq. Cryst. 40, 711 (2013)
- 36 A. Muthusamy and co-workers, J. Polym. Sci., Part A, 51, 1707 (2013)
- 37 N. Al-Muaikel and co-workers, Open J. Org. Polym. Mater. 3(1), 19 (2013)
- 38 Aly Kamal and co-workers, Liq. Cryst. 40(11), 1570 (2013)
- 39 Aly Kamal, Liq. Cryst. 40(7), 998 (2013)
- 40 Aly Kamal and co-workers, Eur. Polym. J. 39(5), 1035 (2003)
- 41 K. Balaji and S. C. Murugavel, J. Poly. Sci., Part A., 39(6), 683 (2012)
- 42 M. Uchimura and co-workers, Res. Chem. Intermed. 39, 403 (2013)
- 43 K.-U. Jeong and co-workers, Macromolecules 38, 8333 (2005)
- 44 Q. Guo and co-workers, J. Macromol. Sci. 50, 363 (2011)
- 45 Qian-yue and co-workers, Shenyang Huagong Daxue Xuebao 24, 240 (2010)
- 46 V. Babacan and co-workers, Polym. Int. 59, 749 (2010)
- 47 A. Romo-Uribe and co-workers, Materials Research Society Symposia Proceedings 63 (1967)
- 48 A. Knijnenberg and co-workers, Macromolecules 39, 6936 (2006)
- 49 M. Iqbal and co-workers, J. Polym. Sci., Part A., 47 ( 5 ), 1368 (2009)
- 50 M. Iqbal and co-workers, High Perform. Polym. 26, 381 (2014)
- 51 S. J. Pickens and co-workers, Liq. Cryst. 38, 591 (2011)
- 52 T. S. Chung and S. X. Cheng, J. Polym. Sci, Part A: Polym. Chem. 38, 1257 (2000).
- 53 P. A. Williams and co-workers, Macromolecules 29, 1874 (1996).
- 54 X. Han and co-workers, Macromolecules 29, 8313 (1996)
- 55 J. Mathew and co-workers, Macromolecules 25, 7338 (1992).
- 56 S. X. Cheng, T. S. Chung, and S. Mullick, Chem Eng Sci 54, 663 (1999).
- 57 S. X. Cheng and T. S. Chung, J. Phys. Chem., Part B 103, 4923 (1999).
- 58 J. Liu, F. Rybnikar, and P. H. Geil, J. Polym. Sci., Part B: Polym. Phys. 30, 1469 (1992).
- 59 J. Liu, F. Rybnikar, and P. H. Geil, J. Macromol. Sci., Part B: Phys. 35, 375 (1996).
- 60 A. Lucero and co-workers, Polymer 38, 4387 (1997).
- 61 F. Rybnikar, B. L. Yuan, and P. H. Geil, Polymer 35, 1831 (1994).
- 62
S. X. Cheng, T. S. Chung, and S. Mullick, J. Polym. Sci., Part B: Polym. Phys.
37, 3084 (1999).
10.1002/(SICI)1099-0488(19991101)37:21<3084::AID-POLB17>3.0.CO;2-Y CAS Web of Science® Google Scholar
- 63 S. X. Cheng and T. S. Chung, J. Polym. Sci., Part B: Polym. Phys. 38, 2221 (2000).
- 64 T. S. Chung and K. X. Ma, J. Phys. Chem., Part B 103, 108 (1999).
- 65 C. Viney and W. S. Putnam, Polymer 36, 1731 (1995).
- 66 W. Wang, G. Lieser, and G. Wegner, Makromolekulare Chemie 194, 1289 (1993).
- 67 J. Wang, S. Bhattacharya, and M. M. Labes, Macromolecules 24, 4942 (1991).
- 68 S. Chen and co-workers, Liq. Cryst. 13, 365 (1993).
- 69 W. Wang, Liq. Cryst. 19, 251 (1995).
- 70 C. Liu, and M. Muthukumar, J. Chem. Phys. 106, 7822 (1997).
- 71 D. K. Ding and E. L. Thomas, Mol. Cryst. Liq. Cryst. 241, 103 (1994).
- 72 J. Gunther and co-workers, Polymer 39, 4497 (1998).
- 73 S. X. Cheng and T. S. Chung, Investigation of the Effect of Lateral Group on Liquid Crystallinity, in preparation.
- 74 C. He and co-workers, J. Polym. Sci., Part A: Polym. Chem. 39, 1242 (2001).
- 75 H. Sato and co-workers, J. Anal. Appl. Pyrolysis 37, 173 (1996).
- 76 D. O. Hummel and co-workers, Makromolekulare Chemie 194, 1545 (1993).
- 77
X. Jin and T. S. Chung, J. Appl. Polym. Sci.
73, 2195 (1999).
10.1002/(SICI)1097-4628(19990912)73:11<2195::AID-APP17>3.0.CO;2-3 CAS Web of Science® Google Scholar
- 78 T. S. Chung and X. Jin, Polymer Engineering and Science 40, 841 (2000).
- 79 K. P. Pramoda and A. Yamaguchi, Polym. Degrad. Stab. 67, 365 (2000).
- 80 M. Avrami, J. Chem. Phys. 7, 1103 (1939).
- 81
M. Avrami, J. Chem. Phys.
212 (1940).
10.1063/1.1750631 Google Scholar
- 82 M. Jaffe, J. D. Menczel, and W. E. Bessey, in E. A. Turi, ed., Thermal Characterization of Polymeric Materials, Academic Press, San Diego, Calif., 1997. Chapt. 2.
- 83 S. Z. D. Cheng and co-workers, Macromolecules 22, 4240 (1989).
- 84 S. Z. D. Cheng and co-workers, Macromolecules 23, 1196 (1990).
- 85 J. Blackwell, H. M. Cheng, and A. Biswas, Macromolecules 21, 39 (1988).
- 86 N. D. Field and co-workers, Macromolecules 21, 2155 (1988).
- 87 T. S. Chung and co-workers, J. Appl. Polym. Sci. 72, 1139 (1999).
- 88 T. S. Chung and co-workers, Polymer Engineering and Science 39, 953 (1999).
- 89 K. P. Pramoda and T. S. Chung, Polym. Prepr. 41, 1391 (2000).
- 90 H. R. Kricheldorf and N. Probst, High Perform. Polym. 7, 471 (1995).
- 91 H. R. Kricheldorf and M. Gurau, J. Polym. Sci., Part A: Polym. Chem. 33, 2241 (1995).
- 92 H. R. Kricheldorf, Advances in Polymer Science, Springer-Verlag, Berlin, 1999, Vol. 141, p. 83.
- 93
S. L. Liu and co-workers, J. Polym. Sci., Part B: Polym. Phys.
36, 1679 (1998).
10.1002/(SICI)1099-0488(19980730)36:10<1679::AID-POLB9>3.0.CO;2-K CAS Web of Science® Google Scholar
- 94 S. L. Liu and co-workers, Polymer Engineering and Science 38, 1845 (1998).
- 95 S. L. Liu and co-workers, J. Polym. Sci., Part B: Polym. Phys. 38, 3018 (2000).
- 96
K. X. Ma, T. S. Chung, and R. J. Good, J. Polym. Sci., Part B: Polym. Phys.
36, 2327 (1998).
10.1002/(SICI)1099-0488(19980930)36:13<2327::AID-POLB8>3.0.CO;2-P CAS Web of Science® Google Scholar
- 97
T. S. Chung, K. X. Ma, and M. Jaffe, Macrom. Chem. Phys.
199, 1013 (1998).
10.1002/(SICI)1521-3935(19980601)199:6<1013::AID-MACP1013>3.0.CO;2-4 CAS Web of Science® Google Scholar
- 98 D. K. Owens and R. C. Wendt, J. Appl. Polym. Sci. 13, 1741 (1969).
- 99 D. H. Kaelble, J. Adhesn. 2, 50 (1970).
- 100 C. J. van Oss, M. K. Chaudhury, and R. J. Good, Chem Rev 88, 927 (1988).
- 101 C. J. van Oss and co-workers, J. Colloid Interface Sci. 128, 313 (1989).
- 102 K. X. Ma and T. S. Chung, J. Phys. Chem. B 105, 4145 (2001).
- 103
P. G. de Gennes and J. Prost. The Physics of Liquid Crystals, Clarendon Press, New York, 1993.
10.1093/oso/9780198520245.001.0001 Google Scholar
- 104 S. Chandrasekhar, Liquid Crystals. Cambridge University Press, Cambridge, UK, 1977.
- 105 L. C. Sawyer and M. Jaffe, J. Mater. Sci. 21, 1897 (1986)
- 106 T. S. Chung, J. Polym. Sci., Polym. Lett. Ed. 24, 299 (1986).
- 107 T. S. Chung, J. Polym. Sci., Part B: Phys. 26, 1549 (1988).
- 108
Y. Ide and T. S. Chung, J. Macromol. Sci., Part B: Phys.
23, 497 (1985).
10.1080/00222348408219473 Google Scholar
- 109 L. C. Sawyer and co-workers, Journal of Materials Science Letters 11, 69 (1992)
- 110 L. C. Sawyer and co-workers, J. Mater. Sci. 28, 225 (1993)
- 111 A. Reyes-Mayer and co-workers, MRS Online Proc. Lib. 1485 (2013)
- 112 A. Reyes-Mayer and co-workers, Polym. Adv. Technol. 27, 748 (2016)
- 113 A. Romo-Uribe and co-workers, Journal of Rheology 41, 1117 (1997)
- 114 A. Siegmann, A. Dagan, and S. Kenig, Polymer 26, 1325 (1985).
- 115 T. S. Chung, Plast. Engi. 43, 39 (1987).
- 116 G. Kiss, Polymer Engineering and Science 27, 410 (1987).
- 117 S. G. James, A. M. Donald, and W. A. Macdonald, Mol. Cryst. Liq. Cryst. 153, 491 (1987).
- 118 T. M. Malik, P. J. Carreau, and N. Chaplea, Polymer Engineering and Science 29, 600 (1990).
- 119 D. Dutta and R. A. Weiss, in D. N. Schulz and J. E. Glass, eds. Polymers as Rheology Modifiers, American Chemical Society, Washington, D.C., 1991, p. 145.
- 120 D. Beery, S. Kenig, and A. Siegmann, Polymer Engineering and Science 31, 451 (1991)
- 121 A. Mehta and A. I. Isayev, Polymer Engineering and Science 31, 971 (1991).
- 122 W. C. Lee and A. T. Dibenedetto, Polymer Engineering and Science 32, 400 (1992).
- 123 J. P. D. Souza and D. G. Baird, Polymer 37, 1985 (1996).
- 124 H. Wang and co-workers, Polym. Compos. 21, 114-123 (2000).
- 125 X. Y. Zhao and co-workers, J. Appl. Polym. Sci. 69, 349 (1998).
- 126 X. Y. Zhao and co-workers, J. Appl. Polym. Sci. 76, 1141 (2000).
- 127 H. R. Kricheldorf and A. Gerken, High Perform. Polym. 9, 75 (1997).
- 128 B. Gupta and co-workers, J. Appl. Polym. Sci. 53, 575 (1994).
- 129 Ya. Freidzon, in Abstracts of Conference of Young Scientists of School of Chemistry (in Russian), Moscow State University, 1973, p. 22.
- 130 USSR Patent 525709 (1975), Ya. Freidzon, V. Shibaev, and N. Platé,
- 131 V. Shibaev, Ya. Freidzon, and N. Platé, Doklady Physical Chemistry (Translation of the Physical Chemistry Section of Doklady Akademii Nauk) 227, 400, (1976).
- 132 V. Shibaev, N. Platé, and Ya. Freidzon, ACS Symp.Ser. 74, 33 (1978).
- 133
Ya. Freidzon, V. Shibaev, and N. Platé, Polym. Sci. USSR, 20, 94, (1978).
10.1016/0032-3950(78)90478-1 Google Scholar
- 134 V. Shibaev, Ya. Freidzon, and N. Platé, J. Polym. Sci. Polym. Ch. Ed. 17, 1655, (1979).
- 135 V. Shibaev, Ya. Freidzon, V. Moiseenko, and N. Platé, Eur. Polym. J. 16, 277, (1980).
- 136 A. Mousa, Ya. Freidzon, V. Shibaev, and N. Platé, Polymer Bulletin 6, 485, (1982)
- 137 Ya. Freidzon, V. Shibaev, N. Boiko, and N. Platé, in A. Blumstein, ed., Polymeric Liquid Crystals, Plenum, New York, (1984, p. 303.
- 138 Ya. Freidzon, N. Boiko, V. Shibaev, and N. Platé, Eur. Polym. J. 22, 13 (1986).
- 139 U.S. Pat. 4,388,453 (1983) H. Finkelmann, G. Rehage, G., and F.-H. Kreuzer.
- 140 T. Bunning and F.-H. Kreuzer. Trends Polym. Sci. 3, 318 (1995).
- 141 F.-H. Kreuzer, N. Haberle, H. Leigeber, R. Maurer, J. Stohrer, and J. Weis, in N. Aurer and J. Weis, eds. Organosilicone Chemistry III, Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, 1998, p. 566.
- 142 M. Ivanov, N. Boiko, E. Chernikova, R. Richardson, X. Zhu, and V. Shibaev, Polym. Sci. A 53, 633, (2011)
- 143 V. Shibaev, Polym. Sci. A 51, 1131 (2009).
- 144 Ya. Freidzon, N. Boiko, V. Shibaev, and N. Platé, Dokl. Akad. Nauk USSR, 282, 939 (1985).
- 145 Ya. Freidzon, Ye. Tropsha, V. Tsukruk, V. Shilov, V. Shibaev, and Yu. Lipatov, Vysokomol. Soedin. A 29, 1371 (1987).
- 146
V. Shibaev, Ya. Freidzon, and S. Kostromin, in V. Shibaev, and Lui Lam, eds., Liquid Crystalline and Mesomorphic Polymers, Springer-Verlag, New York, 1994, p. 77.
10.1007/978-1-4613-8333-8_3 Google Scholar
- 147 J. Goodby, A. Slaney, C. Booth, I. Nishiyama, J. Vuijk, P. Styring, and K. Toyne, Mol. Cryst. Liq. Cryst., 243, 231 (1994).
- 148 J. Goodby, D. Dunmer, and P. Coolings. Liq. Cryst. 19, 703 (1995).
- 149 A. Collyer, ed. Liquid Crystal Polymers: From Structures to Applications, Elsevier Applied Science, London , 1992.
- 150 USSR Pat. 1378345+, (1986) Ya. Freidzon, N. Boiko, V. Shibaev, and N. Platé.
- 151 N. Platé, Ya. Freidzon, and V. Shibaev, Pure Appl. Chem. 57, 1715, (1985).
- 152 Ya. Freidzon, N. Boiko, V. Shibaev, and N. Platé, Eur. Polym. J. 22, 13, (1986).
- 153
Ya. Freidzon, and V. Shibaev, in N. Plate, ed., Liquid-Crystal Polymers, New York: Plenum Press, (1993), p. 251
10.1007/978-1-4899-1103-2_7 Google Scholar
- 154
N. Boiko, Ya. Freidzon, V. Shibaev, and N. Platé, Polym. Sci. USSR, 32, 2463, (1990).
10.1016/0032-3950(90)90420-B Google Scholar
- 155 USSR Pat. 1691803 (1988) Ye. Batyaev, N. Boiko, P. Klyushkin, Ya. Freidzon, and V. Shibaev.
- 156 V. Shibaev, S. Kostromin, and S. Ivanov, Polym. Sci. A 39, 36 (1997).
- 157 V. Shibaev, A. Bobrovsky, and N. Boiko, J. Photochem. Photobiol. A 155, 3, (2003).
- 158 P. Shibaev, N. Boiko, A. Bobrovsky, and V. Shibaev, Polym. Sci. A 47, 590, (2005). .
- 159 V. Shibaev, A. Bobrovsky, and N. Boiko, Polym. Sci. C 42, 103, (2000).
- 160 J. Yu, M. Nakoyo, and T. Ikeda, Pure Appl. Chem. 76, 1467, (2004).
- 161 T. Ikeda, J. Mamiya, and J. Yu, Angew. Chem., Int. Ed. 46, 506, (2007).
- 162 A. Bobrovsky, A. Ryabchun, and V. Shibaev. J. Photochem. Photobiol., A 218, 137, (2011).
- 163 A. Bobrovsky and V. Shibaev, Adv. Funct. Mater. 12, 367, (2002).
- 164 A. Bobrovsky, N. Boiko, V. Shibaev, and J. Wendorff, Advanced Materials 15, 282, (2003).
- 165 V. Shibaev, A. Bobrovsky, and N. Prog. Polym. Sci. 28, 729, (2003).
- 166 A. Bobrovsky and V. Shibaev, J. Mater. Chem. 19, 366, (2009).
- 167 U.S. Pat. 7,344,762 (2008) R. Hammond-Smith, J. Patrick, R. Riddle,
- 168 U.S. Pat. 7,495,740 (2009) R. Hammond-Smith, J. Patrick, R. Riddle, M. Kuntz, M. Ukelis, P. Schmitt, S. Schmltzer.
- 169 U.S. Pat. 8,021,571 (2011) A. May, O. Parri.
- 170 U.S. Pat. 8,334,393 (2012) M. Goldfinger, J. Rodriguez-Parada, L. Silverman, K. Qi.
- 171 U.S. Pat. 8,344,175 (2013) M. Goldfinger, J. Rodriguez-Parada, L. Silverman.
- 172 U.S. Pat. 9,315,729 (2016) M, Wittek, N. Tanaka, A. Taugerbeck.
- 173 V. Shibaev. Polym. Sci. A 56, 727, (2014).
“Liquid Crystalline Polymers” in EPSE 2nd ed., Vol. 9, pp. 1–61, by S. L. Kwolek, E. I. du Pont de Nemours & Co., Inc., P. W. Morgan and J. R. Schaefgen, Consultants.
