pubs.acs.org/Langmuir © 2009 American Chemical Society
Novel Preparation and Characterization of Cellulose Microparticles Functionalized in Ionic Liquids Chun-xiang Lin,† Huai-yu Zhan,† Ming-hua Liu,†,‡ Shi-yu Fu,*,† and Lucian A. Lucia§ †
State Key Laboratory of Pulp & Paper Engineering, South China University of Technology, Guangzhou 510640, China, ‡College of Environment & Resources, Fuzhou University, 350002, China, and § Laboratory of Soft Materials & Green Chemistry, Department of Wood & Paper Science, North Carolina State University, Raleigh, North Carolina 27695-8005 Received March 11, 2009. Revised Manuscript Received April 24, 2009 Ionic liquid (IL)-reconstituted acrylic acid (AA)-functionalized cellulose microparticles were successfully prepared by a water-in-oil suspension technique preliminary modification with AA in homogeneous condition. Cellulose was fully dissolved in 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) IL, and subsequently was grafted homogeneously with AA and N,N0 -methylenebisacrylamide (N,N0 -MBA) initiated with ammonium persulfate. The grafted cellulose was spheroidized using white silicone oil as the dispersion medium and Span 80 as a dispersant and then reconstituted from [Bmim]Cl. Reaction conditions were optimized to obtain microparticles with both the highest possible grafting efficiency and most uniform bead sizes. Fourier transform infrared spectroscopy, scanning electron microscopy, and an optical microscope were employed to provide structural information for the functionalized IL-reconstituted cellulose microparticles. These microparticles were shown to behave as good sorbents for Cu(II), Ni(II), Fe(III) ions.
Introduction Cellulose is among the most promising and novel raw commodity materials available for industrially-relevant chemical and energy transformations by virtue of its massive abundance and, more importantly, renewable nature. Additionally, it is nontoxic, biodegradable, and may be chemically altered to provide new, functionally specific products. Cellulose is not soluble in water or conventional organic solvents because of its well-developed intermolecular hydrogen bonding network. Therefore, commercial cellulose derivatives used nowadays are typically chemically manufactured under heterogeneous conditions, under which the reactivity of cellulose is not compared with that under homogeneous reaction conditions because of the low accessibility of hydroxyl (OH) groups. These hurdles are clearly controlled by hydrogen bond-breaking activation steps such as immersion in alkaline media or by interaction with the appropriate reaction media. Such steps may permit effective synthesis of cellulose products with desired degrees of reactivity, reproducible substitution patterns, and targeted properties both at the laboratory and industry scales;1 moreover, through homogeneous reactions, the reaction rate may also be accelerated. To achieve homogeneous cellulose derivatization reactions, suitable solvent systems that can both dissolve cellulose and provide a feasible reaction environment are prerequisites. The discovery of novel solvents and solution complexes for cellulose over the past three decades has provided opportunities for the application of significantly more diverse synthesis pathways and derivative types.2 For example, various cellulose derivatives have been successfully synthesized through homogeneous methods by the use of N,N-dimethylacetamide (DMAc)/lithium *Corresponding author. (1) Klemm, D.; Heublein, B.; Fink, H. P. Angew. Chem., Int. Ed. 2005, 4(22), 358–3393. (2) Heinze, T.; Liebert, T. Prog. Polym. Sci. 2001, 26(9), 1689–1762. (3) McCormick, C. L.; Dawsey, T. R.; Newman, J. K. Carbohydr. Res. 1990, 208, 183–191.
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chloride (LiCl)3-6 and dimethyl sulfoxide (DMSO)/tetrabutylammonium fluoride trihydrate (TBAF)7,8 solvent systems. However, these solvents have the following limitations: volatility, toxicity, cost, difficulty in recovery, and application instability. More recently, room-temperature ionic liquids (ILs), universally acclaimed as desirable green solvents, have been successfully used to dissolve and process cellulose.9 As novel nonderivatizing cellulose solvents, ILs have also been found to be promising reaction media for cellulose derivatization.10,11 ILs such as 1-butyl-3-methylimidazolium chloride (BmimCl)10 and 1-allyl-3methylimidazolium chloride (AmimCl)11 have been used as reaction media for the acetylation of cellulose and cellulose acetates with varying degrees of substitution (DS) ranging from 1 to 3 in one step. Chemical modification of cellulose through graft copolymerization has also been demonstrated to be a promising method for the preparation of new materials, enabling the introduction of special properties into these abundant biopolymers without destroying their intrinsic characteristics and enlarging their fields of potential applications. The graft copolymerization of vinyl monomers onto cellulose has been widely investigated.12-16 Specifically, acrylic monomers appear to be suitable because of (4) McCormick, C. L.; Callais, P. A. Polymer 1987, 28(13), 2317–2323. (5) Schaller, J.; Heinze, T. Macromol. Biosci. 2005, 5(1), 58–63. (6) Tosh, B.; Saikia, C. N.; Dass, N. N. Carbohydr. Res. 2000, 327(3), 345–352. (7) Ass, B. A. P.; Frollini, E.; Heinze, T. Macromol. Biosci. 2004, 4(11), 1008– 1013. (8) Hussain, M.A.; Liebert, T.; Heinze, T. Macromol. Rapid Commun. 2004, 25 (9), 916–920. (9) Swatloski, R. P.; Spear, S. K.; Holbrey, J. D.; Rogers, R. D. J. Am. Chem. Soc. 2002, 124(18), 4974–4975. (10) Heinze, T.; Schwikal, K.; Barthel, S. Macromol. Biosci. 2005, 5(6), 520–525. (11) Wu, Y.-B.; Yu, S.-H.; Mi, F.-L. Carbohydr. Polym. 2004, 57(4), 435–440. (12) Gupta, K. C.; Sahoo, S. Biomacromolecules 2001, 2, 239–247. (13) Gupta, K. C.; Khandekar, K. Biomacromolecules 2003, 4, 758–765. (14) Roman-Aguirre, M.; Marquez-Lucero, A.; Zaragoza-Contreras, E. A. Carbohydr. Polym. 2004, 55(2), 201. (15) Gupta, K. C.; Sahoo, S. J. Appl. Polym. Sci. 2000, 76(6), 906. (16) Gupta, K. C.; Sahoo, S.; Khandekar, K. Biomacromolecules 2002, 3(5), 1087.
Published on Web 05/20/2009
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the water-repellency and optical transparency of their resultant polymers. The copolymers have been widely used as sorbents for a variety of metal contaminants. However, the mechanical strength of these copolymers is poor and not suitable for a column system.17 To overcome such deficiencies, several methods have been proposed.18,19 In addition, there are many methods to prepare high surface area (spherical) cellulose sorbents, but they suffer from fatal disadvantages such as difficulty of production scale-up and processing the ensuing waste treatment. Therefore, it has remained a challenge to obtain chemically modified cellulosebased sorbents with acceptable mechanical properties. This research presents for the first time the homogeneous graft copolymerization of cellulose in [Bmim]Cl to ultimately provide IL-reconstituted functionalized cellulose microparticles by a water in oil (W/O) suspension technique. The effect of reaction parameters, such as monomer concentration, initiator dosage, reaction time, and reaction temperature on the grafting percentage is given in this report as well as the absorption of selected metal ions.
Experimental Section Materials. Cotton linter was used as received. The IL 1-Nbutyl-3-methylimidazolium chloride ([Bmim]Cl, mp 73°), was purchased from Henan Lihua Pharmaceutical Co., Ltd. All other reagents were of analytical grade and used as received. Dissolution of Cellulose. The dissolution of cellulose was carried out according to the literature.20 Unpretreated cellulose was added to [Bmim]Cl in a three-neck flask. The mixture of cellulose/IL was stirred at 90° up to 12 h to guarantee the complete dissolution of the cellulose. The flask was continuously purged with gaseous N2.
Grafting of Cellulose with Acrylic Acid (AA) in Homogeneous Conditions. After completely dissolving, the tempera-
ture was lowered to 40-80 °C, then a solution of ammonium persulfate (APS) in DMSO, the initiator, was added; after stirring for 15 min, a predetermined volume of partially neutralized AA and a predetermined volume of N,N0 -methylenebisacrylamide (N,N0 -MBA) in DMSO solution, the cross-linker, were added to the reaction, respectively. The polymerization reaction was allowed to occur under specific temperatures and times. Spheroidizing of Cellulose-g-AA/IL. After the graft copolymerization reaction, the mixture of cellulose-AA/IL was slowly added to a white silicone oil (preheated to approximately 80 °C) containing a specific amount of Span 80, a dispersant, and stirred for 30 min to disperse the mixture homogeneously. Then the temperature was allowed to equilibrate to room temperature and was continuously stirred for several hours until the cellulose-AA/IL was cool enough to prevent agglomeration of the microparticles. When the reaction was completed, the solution was removed from the stirrer, and the microparticles were filtered and isolated from IL by precipitation into excess deionized water, filtered, washed several times, and washed with a mixture of methanol-water (30/70 v/v) to remove unreacted monomer. After extraction with acetone for 24 h at room temperature to remove homopolymer, the microparticles were freeze-dried. Grafting Percentage and Grafting Efficiency. Grafting percentage (GP) and grafting efficiency (GE) were calculated by the following equations: GP ¼ ðW 2 -W 0 Þ=W 0 100 GE ¼ ðW 2 -W 0 Þ=W 1 100 (17) Zou, H.; Luo, Q.; Zhou, D. J. Biochem. Biophys. Methods 2001, 49(1-3), 199–240. (18) Guo, W.; Shang, Z.; Yu, Y. J. Chromatogr. A 1994, 685(2), 344–348. (19) Kubota, N.; Nakagawa, Y.; Eguchi, Y. J. Appl. Polym. Sci. 1996, 62(8), 153–1160. (20) Swatloski, R. P.; Spear, S. K.; Holbrey, J. D. J. Am. Chem. Soc. 2000, 124, 4974–4975.
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where W0, W1, and W2 are the weight of the raw cellulose, weight of monomer, and weight of the microparticles after the homopolymers were removed, respectively.
Characterization of the Microparticles Fourier Transform Infrared (FT-IR) Analysis. IR spectra were recorded on a Spectrum GX infrared spectrophotometer (PE Company, USA) using KBr pellets. Scanning Electron Microscopy (SEM) Observation. SEM images of cellulose and functionalized microparticles were obtained by a FEIQUANTA200 scanning electron micrograph machine (Holland Philips Co.). Optical Microscopy. The external appearance of the microparticles was analyzed by a BX51 optical microscope (OLYMPUS Company, USA). Absorption of Soluble Metal Ions from Aqueous Solutions. The absorption capacities of the microparticles were evaluated by a batch method. Three solutions (500 mg/L) of Cu(II), Fe(III), and Ni(II) ions were prepared from analytical-grade copper(II) sulfate, iron(III) nitrate, and nickel(II) nitrate, respectively. Sorption experiments were conducted in a conical flask and equilibrated using a shaker. Then, 50 mL of each of these solutions were separately placed in flasks and equilibrated with 0.1 g of microparticles at room temperature. After 2 h of shaking, the solutions were filtered, and the filtrates were analyzed using a GBC model 902 double beam atomic absorbance spectrophotometer (Victoria, Australia). The results were reported in terms of the amount of metal ions absorbed per gram of the microparticles. The used graft copolymer after absorption was washed twice with 2 mol/L HCl followed by distilled water several times to remove absorbed metal ions. It was reused for further absorption studies.
Results and Discussion Homogeneous Grafting of Cellulose in [Bmim]Cl. Usually, vinyl monomers can be grafted onto cellulose by graft copolymerization through heterogeneous or homogeneous conditions. In heterogeneous systems, grafting occurs only in amorphous regions, causing the number of grafts per cellulose chain to seldom exceed unity.21 The discovery of new solvents of cellulose in the past decades opened the possibility of performing derivatization and/or grafting reactions in homogeneous conditions, thus assuring important advantages, such as better control of the substitution degree, a more uniform distribution of substituents along the polymer chain, and a higher conversion yield. Room-temperature ILs, being considered as desirable green solvents for a wide range of separations and as reaction media for processes including catalysis, have recently received significant attention.22,23 Particularly, when used as reaction media, ILs have several advantages over traditional solvents such as enhancement of reaction rates, improvement of selectivity and yields, and ease of recycling catalysts.24,25 Additionally, the physicochemical properties of ILs may be easily adjusted by changing the structure of cations or anions, which will broaden their application fields. In previous work, dissolution and modification of cellulose in benzylpyridium chloride, ethylpyridium chloride, or their (21) Ogiwara; Kubota Fibre Sci. Technol. 1968, 2, 123–136. (22) Welton, T. Chem. Rev. 1999, 99, 2071. (23) Holbrey, J. D.; Seddon, K. R. Clean Prod. Processes 1999, 1, 223. (24) Earle, M.; Seddon, K. R. ACS Symposium Series 819; American Chemical Society: Washington, DC, 2002; p 10. (25) Gordon, C. M. Appl. Catal. A: Gen. 2001, 222, 101.
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Table 1. Conditions and Results of the Homogeneous Grafting of Cellulose in [Bmim]Cl experiment no. 1 2 3 4 5 6 7 8 9 10
AA/CE (wt) g/g
APS/CE (wt) g/g
temperature/ °C
time/h
GP/%
4 4 4 2 2 2 6 6 6 4
1/30 1/20 1/10 1/30 1/20 1/10 1/30 1/20 1/10 1/10
40 60 80 60 80 40 80 40 60 60
2 3 4 4 2 3 3 4 2 2
56.8 93.2 77.7 22.8 15.5 85.6 32.5 19.7 46.2 96.7
Figure 1. Influence of mass ratio of AA/CE on grafting reaction mass ratio of initiator/CE = 1/10 (g/g), reaction time = 2 h, and reaction temperature = 60 °C.
mixtures with pyridine were reported.26,27 These solvents are similar to current frequently used ILs, except for the relatively high melting points of the former. Recently, dissolution of cellulose with ILs was first reported by Swatloski et al.28 The high concentration of chloride and its activity in ILs are considered to play an important role in cellulose dissolution, by breaking the extensive hydrogen-bonding network present in cellulose. It has been found that [Bmim]Cl is one of the best ILs for dissolving cellulose.29 It has also been found that the dissolution of cotton linters in [Bmim]Cl led to slight degradation, as shown by the DP of cellulose (cotton linter) after regeneration decreasing from 1198 to 812.29 In our work, a solution of 5%(wt) cellulose in [Bmim]Cl was obtained and kept clear and transparent after cooling to room temperature, despite it being highly viscous. The addition of DMSO reduced the viscosity and achieved a completely homogeneous system as the reaction proceeded even at room temperature. To achieve a reasonable reaction speed, a relatively high temperature was adopted. The extent of grafting was evaluated in terms of grafting percentage (GP), which is the ratio of the amount of the introduced side chains to that of the main chain. The GP of AA onto cellulose appeared to be quantitative, judging from the IR spectra and GP of the products as listed in Table 1, which is much higher than 41.3% (prepared under a heterogeneous system30) when reaction conditions were suitable. As summarized in Table 1, the use of the [Bmim]Cl accelerated the reaction rate (96.7% of GP in 2 h, more rapid than the conventional method); further, (26) Forsyth, S.; MacFarlane, D. R.; Thomson, R. J.; Itzstein, M. Chem. Commun. 2002, 714. (27) Graenacher, C. U.S. Patent 1,943,176, 1934. (28) Husemann, E.; Siefert, S. Makromol. Chem. 1969, 128, 288. (29) Swatloski, R. P.; Spear, S. K.; Holbrey, J. D.; Rogers, R. D. J. Am. Chem. Soc. 2002, 124, 4974. (30) Lin, C X. Master paper, 2004.
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Figure 2. Effect of mass ratio of initiator/cellulose mass ratio of AA/CE = 4/1 (g/g), reaction time = 2 h, and reaction temperature = 60 °C.
Figure 3. Effect of reaction time on the graft reaction mass ratio of AA/CE = 4/1 (g/g); mass ratio of initiator/CE = 1/10(g/g), and reaction temperature = 60 °C.
the GP of the products depended on the mass ratio of the AA/ cellulose (CE), the mass ratio of APS/CE, reaction time, and reaction temperature used. Thus, the focus of this investigation has been on the influence of reaction parameters, such as the mass ratio of AA/CE, the mass ratio of APS/CE, reaction time, and reaction temperature. Effect of Monomer. The influence of monomer concentration on the grafting parameters is shown in Figure 1, which illustrates an initial increase followed by a decrease in GP as a function of increasing monomer charge. A maximum is reached when the mass ratio of AA to cellulose is 4 (g/g). This increase is ascribed to the accumulation of monomer molecules close to the cellulose backbone as the monomer concentration increases.21 As the graft copolymerization progresses, the depletion of the available monomer, as well as a reduction in the active sites on the cellulose backbone, results in the subsequent decrease in GP. The continuous decrease of GE (grafting efficiency) with an increase in AA concentration may be associated with the fact that increasing numbers of monomer molecules led to an increase of the likelihood of homopolymerization versus graft copolymerization.22 Effect of Initiator. Figure 2 shows the effect of only the mass ratio of APS to cellulose on the graft copolymerization of AA onto the cellulose backbone as other reaction variables are maintained constant. Both GP and GE show an increase at first, (31) Singh, V.; Tiwari, A.; Narayan, T. D.; Sanghi, R. Polymer 2006, 47(1), 254– 260. (32) Fanta, G. F.; Felker, F. C.; Shogren, R. L. Carbohydr. Polym. 2004, 56(1), 77–84. (33) Lin, O. H.; Kumar, R. N.; Rozman, H. D. Carbohydr. Polym. 2005, 59(1), 57–69. (34) Cui, F.; Qian, F.; Yin, C. Int. J. Pharm. 2006, 316(1-2), 154–161. (35) Sun, T.; Xu, P.; Liu, Q. Eur. Polym. J. 2003, 39(1), 189–192. (36) Gaey, M.; Marchetti, V.; Clement, A.; Loubinoux, B.; Gerardin, P. J. Wood Sci. 2000, 46, 331–333.
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followed by a decrease with an increase in the initiator dosage. The increase of GP may be ascribed to the increase of macroradicals generated by increasing levels of APS (radical initiator) on the glucose unit of cellulose, and therefore, more available sites of cellulose to react with AA. When the mass ratio of APS to cellulose was increased by more than 1/20 (g/g), the concentration of persulfato radicals increased and consequently initiated more of the homopolymerization of AA, which resulted in a decrease in both GP and GE.23 Effect of Reaction Time. As shown in Figure 3, both GP and GE showed a gradual increase with time during the time period of 1 to 2 h and leveled off 2 h later, reaching a saturated grafting value. The reduced monomer and free radicals in the reaction system with an increase in reaction time lead to the leveling off effect.24 Effect of Reaction Temperature. The effect of reaction temperature on graft copolymerization of AA onto cellulose was investigated by changing the temperature from 40 to 80 °C, while keeping other reaction variables constant. Figure 4 shows that both GP and GE reached a maximum at 60 °C. The reaction between the hydroxyl groups of cellulose and APS did not progress readily when the reaction temperature was too low. A higher temperature was helpful in increasing the bimolecular collisions for APS and cellulose, which led to the increase of cellulose macroradicals, and therefore enhanced the graft copolymerization of AA onto cellulose. On the other hand, GP and GE decreased with a further increase in temperature, probably due to the enhanced possibilities of termination and chain transfer at a relatively higher reaction temperature.25 Spheroidizing of Cellulose-g-AA/IL and Regeneration of the Microparticles. As mentioned in the Introduction, cellulose
Figure 4. Influence of reaction temperature on the graft mass ratio of AA/CE = 4/1 (g/g); mass ratio of initiator/CE = 1/10(g/g), and reaction time = 2 h.
Article
copolymers grafted by acrylic monomers have been widely used as metal adsorbents, water-adsorbents, and so on. However, the mechanical strength of the copolymers is poor and is not suitable for use in a column system. Spheroidization of the copolymer is one of the effective ways to overcome these shortcomings. Therefore, in this work, a reverse suspension technique was adopted using white silicone oil as the dispersion medium and Span 80 as the dispersant. A cellulose-g-AA GP of 97.6% (No. 10 from Table 1) was used for spheroidizing. The optimal conditions were chosen as follows: 4:1 volume ratio of oil and solution, 1.5% of the disperse agent dosage, and 400 r/min agitation speed to obtain microparticles with uniform particle size and spherical in shape. 90.0% of the mass percent of the spherical cellulose microparticles had particle sizes ranging from 0.09 mm to 0.075 mm from application of the above optimum conditions. The optical micrographs of representative microparticles are shown in Figure 7. It can be seen that the microparticles are spherical in shape and uniform in size. In addition, the IL could be quantitatively removed from the microparticles using deionized water, as validated by IR (Figure 5). Characterization of the Microparticles. Figure 5 shows the FT-IR spectra of IL-reconstituted CE (upper) and functionalized microparticles (lower). In can be seen that the FT-IR spectrum of the microparticles (lower) has all the characteristic absorbance signals of cellulose and also signature absorbance bands at 1729 cm-1 and 1266 cm-1 corresponding to the -CdO and C-O groups of the AA, respectively. This result confirmed the introduction of the AA side chain into the cellulose backbone via graft copolymerization.
Figure 5. FT-IR spectra of IL-reconstituted CE (upper) and functionalized microparticles (lower).
Figure 6. SEM images of cellulose (a) and functionalized microparticles (b). Langmuir 2009, 25(17), 10116–10120
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Figure 7. Optical microphotographs of the microparticles. Table 2. Adsorptive Capacities of Microparticles for Listed Metal Ionsa metal ions adsorption capacity(mg/g)
Cu(II) 174.8
Ni(II) 61.2
Fe(III) 63.6
Sorption conditions: Cu(II): ion concentration = 500 mg 3 L-1, pH value 5, sorption time 2.0 h; Ni(II): ion concentration = 300 mg 3 L-1, pH value 8, sorption time = 2.0 h; Fe(III): ion concentration = 200 mg 3 L-1, pH value 3.5, sorption time = 2.0 h. a
The SEM micrograph of cellulose (Figure 6a) illustrates a relatively smooth, continuous structure. After the graft copolymerization reaction, rough morphology of the surface of functionalized microparticles (Figure 6b) is clearly observed. It may arise because of the polar difference between cellulose and AA and the interruption of intermolecular hydrogen bonds and crystalline regions in cellulose. Representative optical microphotographs of the microparticles are depicted in Figure 7. It can be observed that the microparticles are spherical in shape and uniform in size (Figure 7b) with an average diameter of approximately 90 μm. Metal Ion Adsorption Capacity of the Microparticles. The high-GP cellulose microparticles functionalized with AA were then used to test the adsorpive capacity toward metal ions in aqueous solution. The results are summarized in Table 2. The data shows that the functionalized microparticles were found to have significant absorbing power for metal ions, demonstrating 174.8, 61.2, and 63.6 mg/g of adsorptive capacity for Cu(II), Ni(II), and Fe(III) of 500 mg/L solutions at pH 5, pH 8, and pH 4, respectively, which is higher than what has been previously reported.36 After removal of absorbed ions by washing twice with 2 mol/L HCl and repeatedly with water, the reconstituted grafted cellulose was found to have 170.2, 58.2, and 60.7 mg/g absorptive capacity for the Cu(II), Ni(II) and Fe(III) cations, respectively, showing that the absorbed metal ions could be relatively easily removed and that the grafted cellulose can be regenerated and reused. The
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designed system therefore has the potential to be used as a possible effective remediation agent for wastewater metal contaminants.
Conclusions Functionalized IL-reconstituted cellulose microparticles were successfully prepared by a water-in-oil suspension technique after homogeneous graft copolymerization using AA in [Bmim]Cl. The impact of polymerization variables including monomer concentration, initiator amount, reaction time, and reaction temperature on grafting was investigated. The GP of the cellulose reached 96.7% when the reaction conditions were as follows: mass ratio of AA/CE = 4/1 (g/g); mass ratio of initiator/CE = 1/10 (g/g); reaction time = 2 h; and reaction temperature = 60 °C. Finally, 90.0% of the mass percentage of the microparticles had particle sizes ranging from 0.09 to 0.075 mm and were obtained by a reverse-phase suspension technique using white silicone oil as the dispersion medium and Span 80 as the dispersant. The FT-IR spectrum and the SEM image of microparticles confirmed the existence of a chemical bond between CE and AA. The optical microscope photographs of the microparticles show that the microparticles are spherical in shape and also have good uniformity. The functionalized microparticles obtained with high GP behaved as good sorbents for metal ions, thus showing their potential for metal ion removal and quite possibly for other related remediation functions. Acknowledgment. The research was financially supported by Program for Changjiang Scholars and Innovative Research Team in University (IRT0552), Fund of China Post Doctor (20070410238), and National High Technology Research and Development Program of China (No. 2007AA100704). We also acknowledge an SCUT-NCSU scholar exchange program that allowed portions of this work to be possible.
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