| Exploring Factors that Determine Cis/Trans Structure and Tacticity in Polymers Prepared by Ring Opening Metathesis Polymerizations Involving Initiators of the Type Syn and Anti Mo(NAr)(CHCMe2Ph)(OR)2. Observation of a Temperature Dependent Cis/Trans Ratio |
14 JUN 95 |
30 pages |
| Authors:
Richard R. Schrock; Jin-Kyu Lee; Richard O'Dell; John H. Oskam; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
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 | The factors that determine the structure (cis/trans and tacticity) of polymers prepared by ring opening metathesis polymerization (ROMP) Using well- defined initiators of the type Mo(NAryl)(CHCMe2Ph)(OR)2 (Aryl = a substituted aryl group and OR = a variety of alkoxides) have been explored. The main finding is a dependence of cis/trans structure on temperature; at low temperatures (-35 deg C) all cis polymer is formed and at high temperatures (65 deg ... |
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| Polymerization of Enantiomerically Pure 2,3-Dicarboalkoxy Norbornadienes and 5,6-Disubstituted Norbornenes by Well-Characterized Molybdenum ROMP catalysts |
29 OCT 93 |
38 pages |
| Authors:
Richard O'Dell; David H. McConville; Gretchen E. Hofmeister; Richard R. Schrock; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
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| Preparing polymers with a regular primary structure is a prerequisite to ultimately controlling the properties of the bulk polymer in a systematic manner. Polymers prepared by ring-opening metathesis polymerization (ROMP) of norbornenes and norbornadienes employing classical metathesis catalysts are rarely regular. In contrast, it has been shown that 2,3-bis(trifluoromethyl) norbornadiene (NBDF6) and 2,3-dicarbomethoxy norbornadiene (DCMNBD) can be ring- opened with 'well-characterized' catalysts of the type Mo(CHCMe2R')(NAr)(OR)2 (R'= Me, Ph; Ar ... |
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| Rotational Isomers of Mo(VI) Alkylidene Complexes and Cis/Trans Polymer Structure: Investigations in Ring-Opening Metathesis Polymerization |
20 OCT 93 |
49 pages |
| Authors:
John H. Oskam; Richard R. Schrock; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
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| In the last few years well-defined metathesis catalysts of the general type M(NR)(CHR)(OR')2 (M=Mo or W) have proven useful in a variety of olefin metathesis studies, in part because the activity of catalysts can be varied systematically by altering the electron-withdrawing ability of the alkoxides. Complexes containing t-butoxides (OCMe3 and OCMe(Cf3)2 in particular) , an arylimido ligand (often NAr, where Ar= 2,6-i-Pr2C6H3), and molybdenum have been the most versatile. In ... |
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| Synthesis of Chiral Molybdenum ROMP Initiators and all-Cis Highly Tactic Poly-2,3-R2Norbornadiene (R = CF3 or CO2Me) |
30 APR 93 |
11 pages |
| Authors:
David H. McConville; Jennifer R. Wolf; Richard R. Schrock; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
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| Well-defined molybdenum ROMP catalysts that contain C2-symmetric diolate ligands (tartrates, binaphtholates, or biphenolates) have been prepared and shown to polymerize 2,3-R2norbornadienes (R = CF3 or CO2Me) to give, in the most favorable case, >99% cis polymers that are >>99% tactic.... ROMP (Ring Opening Metathesis Polymerization), Tartrates, Binaphtholates, Biphenolates, Cis polymers, Norbornadienes. |
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| Synthesis and Side Chain Liquid Crystal Polymers by Living Ring Opening Metathesis Polymerization. 5. Influence of Mesogenic Group and Interconnecting Group on the Thermotropic Behavior of the Resulting Polymers |
22 JUL 92 |
38 pages |
| Authors:
Zen Komiya; Richard R. Schrock; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
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| Norbornene derivatives containing 4'-cyano-4-biphenyloxy mesogens linked to the norbornene through methylene groups (n = 3-7, 9-12) and an ester were polymerized by Mo(CHR)(NAr)(O-t-Bu)2 (Ar = 2,6-C6H3-i-Pr2, R = t-Bu) in a living manner. Polymers in which n = 3 were amorphous, whereas all other polymers (n = 4-7, 9-12) displayed enantiotropic nematic mesophases that were independent of the molecular weight. Polymers having 9-12 methylene spacers did not undergo side chain ... |
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| Rate of Interconversion of Syn and Anti Rotamers of Mo(CHCMe2Ph)(NAr) (OR)2 and Relative Reactivity Toward 2,3-Bis(trifluoromethyl)norbornadiene |
01 MAY 92 |
15 pages |
| Authors:
John H. Oskam; Richard R. Schrock; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
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| Anti rotamers of Mo(CHCMe2Ph)(NAr)(OR)2 complexes (Ar = 2,6-C6H3-i- Pr2; OR = OCMe2(CF3), OCMe(CF3)2 , and OC(CF3)2(CF2CF2CF3)) can be generated at -80 deg in toluene by photolysis at 366 nm and the rate of conversion of anti to syn rotamers determined by NMR methods. At equilibrium the anti rotamers can be observed by high field proton NMR at 250 after many transients and values for Keq(syn/anti) thereby determined. Keq can be ... |
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| Synthesis of Side Chain Liquid Crystal Polymers by Living Ring Opening Metathesis Polymerization. 4. Synthesis of Amorphous and Side Chain Liquid Crystal AB Block Copolymers |
01 MAY 92 |
27 pages |
| Authors:
Zen Komiya; Coleen Pugh; Richard R. Schrock; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
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| Diblock copolymers with well defined block length yield ordered phase separation. Morphology of the microphase separation is controllable by varying the weight ratio of the two blocks and the length of each block. If one of the blocks is a side chain liquid crystalline polymer (SCLCP), microphase separated systems with liquid crystalline crystalline microphases may be realized. Such systems are of fundamental as well as practical interest. The effect of ... |
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| Synthesis of Side Chain Liquid Crystal Polymers by Living Ring Opening Metathesis Polymerization. 3. Influence of Molecular Weight, Interconnecting Unit and Substituent on the Mesomorphic behavior of Polymers with Laterally Attached Mesogens |
08 APR 92 |
50 pages |
| Authors:
Coleen Pugh; Richard R. Schrock; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
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| Norbornene derivatives containing laterally attached 2,5-bis(4'-n- alkoxybenzoyl OXY) mesogens were polymerized by controlled ring opening metathesis polymerization to provide polymers in high yield with 5-100 repeat units and narrow molecular weight distributions. Monomers with n>l displayed monotropic or enantiotropic nematic mesophases. All polymers displayed enantiotropic nematic mesophases regardless of the spacer, molecular weight or length or the n-alkoxy substituent. Constitutional isomers of poly(5-carbo(2', 5'-bis-4( methoxybenzoyloxy)benzyloxy)bicyclo(2.2.1)hep t-2-ene)s containing laterally attached mixed ... |
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| Synthesis of Side Chain Liquid Crystal Polymerization by Living Ring Opening Metathesis Polymerization. 1. Influence of Molecular Weight, Polydispersity, and Flexible Spacer Length (n=2-8) on the Thermotropic behavior of the Resulting Polymers |
31 MAR 92 |
39 pages |
| Authors:
Zen Komiya; Coleen Pugh; Richard R. Schrock; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
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| The living ring opening metathesis polymerization of 5-carbo(n-(4'- methoxy-4-biphenylyl)oxy)alkyl)bicyclo(2.2.1)hept-2-ene (1-n, n=2-8) by Mo(CH-t- Bu)(NAr) (0-t-Bu)2(Ar=2,6-C6H3-t-Pr2) is described. Polymers with degrees of polymerization from 5 to 100 and narrow molecular weight distributions (Mw/Mn=1. 05-1.24) were obtained in high yield. All polymers exhibit an enantiomorphic nematic mesophase. Glass transition and isotropization temperatures increase with increasing molecular weight and become independent at approximately 30-50 repeat units. The change in enthalpy of isotropization is ... |
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| Synthesis of Side Chain Liquid Crystal Polymers by Living Ring Opening Metathesis Polymerization. 2. Influence of Molecular Weight, Polydispersity, and Flexible Spacer Length (n=9-12) on the Thermotropic behavior of the Resulting Plymers |
31 MAR 92 |
27 pages |
| Authors:
Zen Komiya; Coleen Pugh; Richard R. Schrock; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
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| The living ring opening metathesis polymerization of 5-carbo(n-(4'- METHOXY-4BIPHENYLYLoxyalkyl)bicylco2.2.1hept-2-ene (1-n, n=9-12) with Mo(CH-t- Bu)(NAr) (0-t-Bu)2 (Ar=2,6-C6H3-i-Pr2) is described. Polymers with degrees of polymerization from 5 to 100 and narrow molecular weight distributions (Mw/Mn=1. 07-1.28) were obtained in high yield. All polymers exhibit side chain crystallization along with a nematic mesophase. Isotropization temperatures increase with increasing molecular weight and then become independent of molecular weight at approximately 30-50 repeat units. Side ... |
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| Ring Opening Metathesis Polymerization |
15 JAN 92 |
6 pages |
| Authors:
Richard R. Schrock; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
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| The central theme of this research is ring opening metathesis polymerization of norbornenes and substituted norbornadienes by well characterized imido alkylidene catalysts of the type M(CHR)(NR')(OR )2 (where R, R', and R are some alkyl or aryl groups), or most recently alkylidyne alkylidene rhenium catalysts of the type Re(CHR)(CR')(OR )2. Initially we focused on developing catalysts that would tolerate functionalities (such as carbonyl groups). The findings concerning the polymerization of ... |
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| Living Ring-Opening Metathesis Polymerization of 7-oxa-2,3- Difunctionalized Norbornenes and Norbornadienes by Mo(CHCMe2R)(N-2,6-C6H3-i-Pr2) (O-t-Bu)2 and Mo(CHCMe2R)(N-2,6-C6H3-i-Pr2)(OCMe2CF3)2 |
18 APR 91 |
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| Authors:
Guillermo C. Bazan; John H. Oskam; Hyun-Nam Cho; Lee Y. Park; Richard R. Schrock; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
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 | An important class of readily prepared norbornenes and norbornadienes are those that contain oxygen in the 7 position. 7-Oxanorbornenes and norbornadienes have been polymerized by Ru and Os-based classical catalysts in ethanol and in water and the resulting polymers have been shown to act as acyclic ionophores. Poly-7-oxa-2,3-dicarbomethoxynorbornadiene also has been reported to be converted into a polyene upon dehydrogenation with DDQ. But from the point of view of mechanistic ... |
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| Potential Dependence of the Conductivity of Polyacetylene: Finite Potential Window of High Conductivity |
MAR 91 |
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| Authors:
David Ofer; Lee Y. Park; Richard R. Schrock; Mark S. Wrighton; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
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| The cyclic voltammetry and the potential dependence of conductivity for polyacetylene films on platinum electrode arrays have been studied in both liquid SO2/electrolyte and tetrahydrofuran/electrolyte. The polyacetylene was prepared by thermolysis of films of films of poly(7,8-bistrifluoromethyl- tricyclo 4.2.2.0 2,5deca-3,7,9-triene) deposited on interdigitated electrode arrays. When oxidized in liquid SO2/electrolyte, polyacetylene has a maximum in conductivity a polyvinylferrocene internal reference, and conductivity is three orders of magnitude lower at +2.0 ... |
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| New Polymers Made with Well-Characterized Organometallic Catalysts |
16 OCT 89 |
4 pages |
| Authors:
Richard R. Schrock; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
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| In the first publication we reported that Mo(CH-t-Bu)(NAr)(O-t-Bu)2 was a good catalyst for the ring opening metathesis polymerization of endo,endo- 5,6-dicarbomethoxynorbornene to give homopolymers with polydispersities in the range 1.11-1.22, as well as block copolymers containing endo,endo-5,6- dicarbomethoxynorbornene and norbornene with similar low polydispersities. In the second publication we reported additional details of the metathesis of functionalized monomers by molybdenum, and also that 7,8-bis(trifluoromethyl) tricyclo(4.2.2.0)deca-3,7,9-triene could be ring opened and ... |
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| Preparation and Reactions of Tantalum Alkylidene Complexes Containing Bulky Phenoxide or Thiolate Ligands. Controlling Ring-Opening Metathesis Polymerization Activity and Mechanism Through Choice of Anionic Ligand |
29 JUL 88 |
69 pages |
| Authors:
Kevin C. Wallace; Andy H. Liu; John C. Dewan; Richard R. Schrock; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
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| We have reported a variety of high oxidation state, electronically unsaturated alkylidyne and (more recently) alkylidene complexes of tungsten and molybdenum that contain bulky alkoxide ligands. We decided to test whether some of the principles we had uncovered in tungsten and molybdenum chemistry could be used to advantage in tantalum chemistry, especially since Ta(CH1Bu)(THF)2Cl3 can be prepared in high yield in two relatively easy steps from TaCl. Tantalum alkylidene complexes ... |
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| Low Polydispersity Homo- and Block Copolymers by Ring-Opening of 5,6- Dicarbomethoxynorbornene |
31 JUL 87 |
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| Authors:
John S. Murdzek; Richard R. Schrock; MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF CHEMISTRY
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| Addition of 50-200 eq of norbornene to Mo(CH Superscript t Bu) (NAr) (O Superscript t Bu)2 yields living polymers, Mo?CH(C5H8)CHxCH Superscript t Bu (NAr)(O Superscript t Bu)2 (55% trans), that are stable for days in the absence of water and oxygen with essentially no isomerization of the double bonds in the chain. Addition of benzaldehyde cleaves off the polymer in a Wittig-like reaction to yield polynorbornenens with polydispersities in the ... |
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