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Synthesis and NMR characterization of 6‐Phenyl‐6‐deoxy‐2,3‐di‐ O ‐methylcellulose
Author(s) -
Nozar D. Sachinvala Navzer,
Winsor David L.,
Hamed Othman,
Niemczura Walter P.,
Maskos Karol,
Vigo Tyrone L.,
Bertoniere Noelie R.
Publication year - 2002
Publication title -
polymers for advanced technologies
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.61
H-Index - 90
eISSN - 1099-1581
pISSN - 1042-7147
DOI - 10.1002/pat.204
Subject(s) - differential scanning calorimetry , glass transition , thermogravimetric analysis , dynamic mechanical analysis , cellulose , materials science , polymer , gel permeation chromatography , polymer chemistry , proton nmr , carbon 13 nmr , nuclear chemistry , decomposition , yield (engineering) , chemistry , organic chemistry , composite material , physics , thermodynamics
Cellulose ( 1 ) was converted for the first time to 6‐phenyl‐6‐deoxy‐2,3‐di‐ O ‐methylcellulose ( 6 ) in 33% overall yield. Intermediates in the five‐step conversion of 1 to 6 were: 6‐ O ‐tritylcellulose ( 2 ), 6‐ O ‐trityl‐2,3‐di‐ O ‐methylcellulose ( 3 ), 2,3‐di‐ O ‐methylcellulose ( 4 ); and 6‐bromo‐6‐deoxy‐2,3‐di‐ O ‐methylcellulose ( 5 ). Elemental and quantitative carbon‐13 analyses were concurrently used to verify and confirm the degrees of substitution in each new polymer. Gel permeation chromotography (GPC) data were generated to monitor the changes in molecular weight (DP w ) as the synthesis progressed, and the compound average decrease in cellulose DP w was ∼ 27%. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to characterize the decomposition of all polymers. The degradation temperatures ( °C) and percent char at 500 °C of cellulose derivatives 2 to 6 were 308.6 and 6.3%, 227.6 °C and 9.7%, 273.9 °C and 30.2%, 200.4 °C and 25.6%, and 207.2 °C and 27.0%, respectively. The glass transition temperature ( T g ) of6‐ O ‐tritylcellulose by dynamic mechanical analysis (DMA) occurred at 126.7 °C and the modulus (E′, Pa) dropped 8.9 fold in the transition from −150 °C to + 180 °C (6.6 × 10 9 to 7.4 × 10 8 Pa). Modulus at 20 °C was 3.26 × 10 9 Pa. Complete proton and carbon‐13 chemical shift assignments of the repeating unit of the title polymer were made by a combination of the HMQC and COSY NMR methods. Ultimate non‐destructive proof of carbon–carbon bond formation at C6 of the anhydroglucose moiety was established by generating correlations between resonances of CH 2 6 (anhydroglucose) and C1′, H2′, and H6′ of the attached aryl ring using the heteronuclear multiple‐bond correlation (HMBC) method. In this study, we achieved three major objectives: (a) new methodologies for the chemical modification of cellulose were developed; (b) new cellulose derivatives were designed, prepared and characterized; (c) unequivocal structural proof for carbon–carbon bond formation with cellulose was derived non‐destructively by use of one‐ and two‐dimensional NMR methods. Copyright © 2002 John Wiley & Sons, Ltd.