ORI GIN AL

Characterization of the surface properties of b-CD-CA-wood flour polymer by inverse gas chromatography

Ting Wang • Hongyan Si • Bin Li

Received: 20 December 2012 / Published online: 24 October 2013

� Springer-Verlag Berlin Heidelberg 2013

Abstract Poplar wood flour, a low-cost and abundantly available material, was

modified by grafting b-cyclodextrin in the presence of citric acid, aiming to expand

the application of wood flour. The product was characterized by Fourier transform

infrared spectroscopy and the technique of the phenolphthalein probe. By the

technique of inverse gas chromatography and the method of Hamieh, the values of

surface free energy and nonpolar part of the free energy were obtained. The results

demonstrate that the dispersive component of the surface free energy of the products

will increase with temperature increases, and the product presents a Lewis basic

character with Kb/Ka = 3.67. Based on the structure of the product, the basicity

comes from two parts. One is the rich electronic environment of the b-CD inner

cavity, and the other is the formation of ester bonds through crosslinking between b-

CD and wood flour by CA.

Introduction

Because of the increasing consumption of conventional energy and the diminishing

supplement of fossil energy, efficient utilization of biomass resources has become a

hot topic of the scientific research (Yoshioka et al. 2005; Zhang and Long 2010).

Wood flour is a kind of biomass resource and usually comes from the waste

products of the timber industry. With the properties of low price, abundance,

renewability, biodegradability, and ease of chemical modification, wood flour is

often used as reinforcing filler in polymer composites to produce wood plastic

compound materials (WPC) (Kazemi-Najafi et al. 2008; Filson et al. 2009; Kord

T. Wang � H. Si � B. Li (&)

Heilongjiang Key Laboratory of Molecular Design and Preparation of Flame Retarded Materials,

Department of Chemistry, Northeast Forestry University, Harbin 150040,

People’s Republic of China

e-mail: libinzh62@163.com

123

Wood Sci Technol (2014) 48:195–206

DOI 10.1007/s00226-013-0594-z

et al. 2011). Whereas, to the authors’ knowledge, few studies are performed on the

functional modification of wood flour and measurement of the surface Lewis acid–

base properties, which are known to contribute significantly to the functionality and

surface interactions in WPC polymer composite systems (Santos and Guthrie

2005a).

b-Cyclodextrins (b-CD) are a supramolecular host of great importance due to

their ability to form inclusion complexes with a wide variety of lipophilic

functional guests (Szetjli 1998). On the basis of their typical encapsulation ability,

many materials have been modified by CDs for obtaining the functional extension,

including carbon nanocrystals (Jiang et al. 2010), bovine pancreatic trypsin

(Fernandez et al. 2004), chiral stationary phases (Lai et al. 2011), nanoparticles

(Freeman et al. 2009), polymer of sulfanilic acid, and N-acetylaniline (Wu et al.

2008), etc. Using b-CD to modify wood flour not only endows wood flour with

extended functional ability (Si et al. 2013), but also expands the application of

b-CD.

The specific properties for a polymer material depend strongly on its surface

energy and specific interaction forces. The usual techniques for measuring surface

acid–base parameters are isoelectric point, indicator dye adsorption, X-ray

photoelectron, calorimetry, and inverse gas chromatography (IGC) (Shi et al.

2007a; Hamieh and Schultz 2002; Hamieh et al. 2002; Santos and Guthrie 2005b).

For polymer materials, IGC technique is more often used to characterize the surface

Lewis acid–base properties than the other methods.

In this study, IGC was used to characterize quantificationally the Lewis acid–

base properties and the dispersive component of surface free energy of b-CD

grafting wood flour by citric acid (b-CD-CA-WF) polymer. The Ka and Kb values,

which describe the Lewis acidity and basicity of the b-CD-CA-WF polymer surface,

were calculated.

Experimental

Materials

Poplar wood flour (100 mesh) was soaked in 20 % (wt%) NaOH for 1 h, then rinsed

thoroughly with 65 �C distilled water, and dried at 80 �C for 24 h. b-CD was

purchased from TCI (Japan). Citric acid (CA) was used as crosslinking agents and

bought from Damas-beta (Switzerland). NaH2PO2�H2O was used as catalysts and

obtained from Tianjin Kermel chemical Reagent Co., Ltd. (China). Na2CO3�10H2O

and NaHCO3 were used to prepare buffer solution (pH = 10.5) and provided by

Tianjin Guangfu Technology Development Co., Ltd. (China). Phenolphthalein and

EG were supplied by Shanghai Aladdin Co., Ltd. (China).

For the IGC analysis, the apolar n-alkane probes were n-pentane(C5), n-hexane

(C6), n-heptane (C7), and n-octane (C8). The polar probes were trichloromethane

(CHCl3), ethyl acetate (Etac), ether, and tetrahydrofuran (THF). They were

analytical grade solvents and purchased from Tianjin Kermel Chemical Reagents

Development Centre, China. Methane was used as the non-interacting probe

196 Wood Sci Technol (2014) 48:195–206

123

purchased from Shanghai Aladdin Co., Ltd. (China). The characteristics of probe

solvents are listed in Table 1.

Preparation of modified wood flour material

Fifty gram of wood flour was impregnated with 500 mL of the aqueous solution

containing b-CD (0–140 g/L), crosslinking agent (100 g/L), and phosphatic catalyst

(30 g/L). To ensure the saturated absorption of the aforementioned mixed solution,

the impregnation of wood flour was performed under ultrasound and shaking for

20 min and stirring for 6 h. After storage overnight, the wood flour was filtrated,

squeezed, pre-dried at 80 �C for 12 h, and cured at different temperatures for 7 min.

In the end, the raw products were sufficiently washed by warm water (60 �C) and

alcohol alternately and dried at 105 �C, and then, the product weight was recorded.

The sample of b-CD grafting onto wood flour through the crosslinker of CA was

designated as b-CD-CA-WF polymer.

Characterization by Fourier transform infrared spectroscopy

Fourier transform infrared spectroscopy (FTIR) experiments were performed on a

Perkin-Elmer Spectrum 400 instrument in the frequency range between

4,000–400 cm-1. All samples were prepared by mixing with KBr powder prior to

the testing.

Determination of the active b-CD

For evaluation of the encapsulation ability of b-CD on the modified wood flour

material, a previous work of phenolphthalein probe technology was applied here

(Wang et al. 2011). The content of b-CD (cCD) could be calculated by Eq. 1.

DA ¼ 1:565cCD þ 0:011 ð1Þ

where DA denotes the difference between the UV absorbance of diluted separation

filtrates and that of b-CD blank (phenolphthalein solutions without addition of b-CD).

Table 1 Characteristics of the probe solvents

Name cdl (mJ/m2) a A

2� �

a �ffiffiffiffifficd

l

qA

2� �

[(mJ/m2)0.5]

AN* (kJ/mol) DN (kJ/mol)

n-C5 16.00 46.1 184

n-C6 17.90 51.5 217.9 – –

n-C7 19.80 57.0 253.6 – –

n-C8 21.14 63.0 289.7 – –

CHCl3 44.0 25.9 224 22.7 0.0

Ether 47.0 15.0 182 5.88 80.6

THF 45.0 22.5 213 2.1 84.4

Etac 48.0 19.6 212.5 6.3 71.1

Wood Sci Technol (2014) 48:195–206 197

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The content of active b-CD on the modified wood flour material was evaluated

by Eq. 2.

Active b-CD content (%) =c� c0ð Þ � 0:1�M

m� 100 % ð2Þ

where c represents the active b-CD concentration of modified wood flour material

(mol/L). c0 represents the b-CD concentration of b-CD blank grafting wood flour

(impregnated solution without addition of b-CD) (mol/L). M represents the b-CD

molecular weight of 1,135 g/mol. m denotes the weight of dry wood floor (g).

Inverse gas chromatography

IGC measurements were taken on a GC-9A gas chromatograph (Shimadzu

Corporation, Japan), that is equipped with a thermal conductivity detector (TCD).

Hydrogen was used as the carrier gas. The flow rate was 30 mL/min, measured from

the end of the column with a soap bubble flow meter. The column used was a

standard stainless steel tube, 200 mm long and an internal diameter of 3 mm.

The column was packed with about 1.2 g of the sample powder with

granulometry lower than 60 meshes. The sample was packed by manual tapping

for 0.5 h, conditioned overnight at 323 K and 30 mL/min of hydrogen flow rate, and

then conditioned for 2 h at the temperature of analyses and 0 % relatively humidity.

After conditioning the columns, the injector and TCD were heated to 160 �C, and

the probe solvents were injected manually using a 5 lL Hamilton syringe; the

injection volumes were 0.5 lL. Methane was the tracer molecule used to calculate

the dead time.

Four n-alkanes (pentane, hexane, heptane, and octane) were used to measure the

dispersive component of the surface energy at four different temperatures, 323, 333,

343, and 353 K. Four polar probes, THF, Etac, Ether, and CHCl3, were used at the

same conditions to study Gibbs specific free energy and acid–base surface character.

The experiments were done five times, and the presented results are the average

values. The experimental error due to the temperature variation, flow rate, and

retention time measurement was estimated to be below 3 %.

Results and discussion

IR analysis

The FTIR spectra of wood flour, b-CD, b-CD-CA-WF washing control and the

target product of b-CD-CA-WF polymer are shown in Fig. 1. Here, b-CD-CA-WF

washing control was prepared in the same way as b-CD-CA-WF polymer except for

the curing procedure. In Fig. 1a, c, and d, the absorption bands at 1,735 and

1,054 cm-1 are attributed to ester carbonyl group and C–O–C group of wood flour,

respectively. Comparing Fig. 1a and d, the proportion of the band intensity at

1,735–1,054 cm-1 of b-CD-CA-WF polymer is higher than that of wood flour.

Compared to Fig. 1a with c, there is no significant difference between the spectra of

198 Wood Sci Technol (2014) 48:195–206

123

wood flour and that of b-CD-CA-WF washing control, which demonstrates that the

adsorbed polycarboxylic acid and b-CD have been removed completely by the

washing procedure. Thus, the increase in the ester carbonyl band in the b-CD-CA-

WF polymer spectrum is not caused by the adsorbed polycarboxylic acid of CA. It is

due to the formation of ester band through successful grafting of CA. In addition,

the bands of b-CD (Fig. 1b) cannot be distinguished from the spectra of b-CD-CA-

WF polymer, because these bands are overlapped by the spectrum of wood flour.

Therefore, the grafting of b-CD on wood flour required another technique for further

prove.

The evaluation of the b-CD encapsulation ability on the b-CD-CA-WF polymer

Due to the phenomenon of purple phenolphthalein (PP) solution becoming colorless

in the presence of b-CD, the surface active b-CD content on the b-CD-CA-WF

polymer has been determined in a previous research work (Wang et al. 2011).

Keeping the pH = 10.5 unchanged, the purple PP solution faded by mixing the b-

CD-CA-WF polymer powder. Until an overnight balance, the surface active b-CD

4000 3500 3000 2500 2000 1500 1000 50050

60

70

80

90

100(b)wood flour

T%

Wavelength (cm-1)

(a)

1735

1054

4000 3500 3000 2500 2000 1500 1000 500

50

60

70

80

90

100β−CD

T%

Wavelength (cm-1)

1029

1646

4000 3500 3000 2500 2000 1500 1000 50050

60

70

80

90

100(c) β−CD-CA-WF washing control

T%

Wavelength (cm-1)

1735

1054 1054

4000 3500 3000 2500 2000 1500 1000 50050

60

70

80

90

100(d) β -CD-CA-WF copolymer

T%

Wavelength (cm-1)

1735

Fig. 1 FTIR spectra of wood flour (a), b-CD (b), b-CD-CA-WF polymer washing control (c), and b-CD-CA-WF polymer (d)

Wood Sci Technol (2014) 48:195–206 199

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content on the b-CD-CA-wood flour polymer was determined as 6.9 ± 0.6 %

(wt%), which not only demonstrates successful grafting of b-CD macromolecules

but also verifies the encapsulating ability of the material of b-CD-CA-WF polymer.

SEM analysis

The SEM images in Fig. 2 indicate the microcosmic pattern of WF and b-CD-CA-

WF polymer. From Fig. 2a, it can be seen that the wood fiber has a relative smooth

surface and fiber texture structure, while in Fig. 2b, the fiber texture structure has

disappeared and turns out to be a lamellar structure. It can be observed that the

cracks on the cellulose fibers are covered by the grafting b-CD in the presence of

CA.

Determination of Lewis acid–base properties

The dispersive component of surface free energy and Lewis acid–base properties of

oxide and hydroxide surfaces is of vital importance in physical chemistry, in

particular in interfacial adhesion research (Schultz et al. 1987; Tsutsumi and Ohsuga

1990; Vangani et al. 1995; Kimura et al. 2000), including interfacial properties of

WPC material (Zhao et al. 2009; Kamdem and Riedl 1991). In this work, the

dispersive component of surface free energy cds of polymeric stationary phase is

measured when n-alkanes are probes. The assumption is that only dispersive

interactions between n-alkanes and polymer exist. cds is obtained from the net

retention volume according to Eq. 3 (Santos et al. 2002; Santos and Guthrie 2005a)

DGda ¼ RT lnðVnÞ ¼ 2NAaðcd

s Þ0:5ðcd

l Þ0:5 þ K ð3Þ

where DGda is the dispersive free energy of adsorption, Vn is the net retention

volume, and cds and cd

l are the dispersive components of the surface tension of the

solid material and the probe molecule, respectively. a is the cross-sectional area of

Fig. 2 SEM pictures of wood flour (a) and b-CD-CA-WF polymer (b)

200 Wood Sci Technol (2014) 48:195–206

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the probe molecule and NA is the Avogadro constant. The constant K is related to the

reference gas pressure and the reference surface pressure. By plotting RT lnðVnÞversus aðcd

l Þ0:5

for the n-alkane probes, the value of cds is calculated with the slope.

The net retention volume Vn was calculated according to Hamieh et al. (2002).

When polar probes are used, dispersive and specific interactions take place. Thus,

the free energy of adsorption, DGa, is decomposed into two components: dispersive

(DGda) and specific (DGs

a), Eq. 4:

DGa ¼ DGda þ DGs

a ð4Þ

DGsa, corresponding to the polar probes, is a measure of how easily the surface can

polarize the probe. DGsa results from the distance between the RT lnðVnÞ value of

polar probe and the straight n-alkane line.

The enthalpy of specific interactions, DHsa, is calculated according to Eq. 5

(Santos et al. 2002; Santos and Guthrie 2005a):

DGsa ¼ DHs

a � TDSsa ð5Þ

where DSsa is the specific entropy of adsorption. DHs

a results from the intercept of the

plot of DGsa versus T.

The Lewis acid number Ka and Lewis base number Kb are calculated according to

Eq. 6 (Santos et al. 2002; Santos and Guthrie 2005a):

� DHsa

AN� ¼ Ka

DN

AN�þ Kb

� �ð6Þ

where DN and AN* are the Gutmann’s Donor and modified acceptor number of

polar solvents, respectively. Plotting DHsa=AN� versus DN/AN* gives Ka as the slope

and Kb as the intercept.

Figure 3 shows the data of ln Vn versus the inverse of the column temperature for

n-alkanes and polar probes. The linear relationships of the plots are good.

According to Eq. (3), the dispersive component of surface free energy cds of the b-

CD-CA-WF polymer is calculated from DGda RT lnðVnÞ½ � of n-alkanes for every

temperature. Figure 4 shows the plots of RT lnðVnÞ versus aðcdl Þ

0:5of n-alkanes at

323, 333, 343, and 353 K, respectively. The results are listed in Table 2. It shows

that the dispersive component of surface free energies increases with increasing

temperatures. This phenomenon is due to the fact that the data in Table 2 are only

the dispersive component of surface free energies instead of the total free energies

which are the sum of dispersive components and Lewis acid–base components (Shi

et al. 2007b).

Figure 5 shows the calculation of the specific free energy of adsorption DGsa for

the polar probes adsorbed on b-CD-CA-WF polymer at 323 K. Table 3 lists the data

of DGsa, which are measured at the overall temperatures.

According to Eq. 5, the enthalpy of specific interactions DHsa for every polar

probe is calculated from specific free energy of adsorption DGsa and the column

temperature listed in Table 3.

Wood Sci Technol (2014) 48:195–206 201

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Fig. 3 Data of ln Vn versus 1,000/T for the probes

Fig. 4 Surface free energy of adsorption versus aðcdl Þ

0:5for n-alkanes

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Then, the Lewis acid–base numbers are calculated according to Eq. (6), and

Fig. 6 shows a plot of DHsa=AN� versus DN/AN* for the polar probes. The linear

regression equation is Y = 0.1214X ? 0.4461, Coefficient of regression is 0.9965.

It shows that the Gutmann’s acid–base concept is valid for the studied systems and

that the specific interactions may be considered due to the electron donor–acceptor

interactions. The obtained constants, describing surface acidity (Ka) and basicity

(Kb) of the b-CD-CA-WF polymer, are 0.1214 and 0.4461, respectively. This result

demonstrates that b-CD-CA-WF polymer exhibits a Lewis basic character by

showing the Kb/Ka = 3.67.

The surface basic character has been discovered on many biomass materials

(Rjiba et al. 2007; Spinace et al. 2009; Cordeiro et al. 2011); however, the basicity

of the material b-CD-CA-WF polymer comes from two parts: One is the rich

electronic environment of the b-CD inner cavity (Szetjli 1998) and the other is the

formation of ester bond through crosslinking between b-CD and wood flour by CA.

Table 2 Dispersive component of surface free energy ðcds Þ

0:5(mJ/m2) of the b-CD-CA-WF polymer

Temperature (K) Equation of linear regression Coefficient of regression ðcds Þ

0:5(mJ/m2)

323 Y = 0.06773X-14.9312 0.9994 31.65

333 Y = 0.07098X-16.6806 0.9993 34.76

343 Y = 0.07278X-18.0873 0.9992 36.54

353 Y = 0.07395X-19.2846 0.9999 37.72

Fig. 5 Free energy of adsorption versus aðcdl Þ

0:5for n-alkanes and polar probes at 323 K

Wood Sci Technol (2014) 48:195–206 203

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A large sum of ether-like oxygens is at the inside of the torus-like b-CD molecule

(Martin 2004), and when the probe molecule contacts the inner cavity of the grafting

b-CD molecule, the modified wood based material demonstrates a Lewis basic

character. However, the size of the probe molecules used in this work is small

enough to contact the inner cavity of b-CD molecule (Szetjli 1998; Hedges 1998);

thus, it is easy to explain the surface basicity of the material b-CD-CA-WF polymer.

The crosslinker of CA is tricarboxylic acid. In the current preparation, the

grafting reaction of b-CD onto wood flour by CA proceeds in two steps: the

formation of a cyclic anhydride intermediate by dehydration of two carboxylic acid

groups and the forming of ester links between b-CD and wood flour by anhydride

intermediate (Yang 1993; Yang and Wang 1997). The oxygen in the ester bond has

a Lewis basic character for the probe molecules, that is, the higher the Kb/Ka ratio

the higher the grafting efficiency. Therefore, the surface of the b-CD-CA-WF

polymer inclined to adsorb Lewis acidic molecules.

Table 3 Specific free energy of adsorption DGsa (kJ/mol) and specific interactions DHs

a (kJ/mol)

Probe Temperature (K) DHsa (kJ/mol)

323 333 343 353

CHCl3 0.718 1.102 1.303 1.737 -9.80

Etac 2.804 3.376 3.803 4.072 -10.79

THF 2.035 2.454 2.893 3.250 -11.156

Ether 0.299 0.766 1.317 1.513 -13.20

Fig. 6 Determination of Ka and Kb for the surface Lewis acid–base of the b-CD-CA-WF polymer

204 Wood Sci Technol (2014) 48:195–206

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Conclusion

IGC is applied to determine the surface properties, namely dispersive surface energy

and acid–base properties. The dispersive component of surface free energies

increases from 31.65 mJ/m2 at 323 K to 37.72 mJ/m2 at 353 K. The Lewis acidic

number Ka and the basic number Kb are 0.1214 and 0.4461, respectively. The inner

cavity of grafting b-CD molecule and the ester bond of the crosslinker are the main

reasons to cause the surface of the b-CD-CA-wood flour polymer exhibiting a Lewis

basic character.

Acknowledgments This study was supported by Fundamental Research Funds for the Central

Universities (DL11BB02), National Natural Science Fund of China (NSFC, NO. 30972423), and

Educational Bureau Scientific Project of Hei Longjiang Province NO. 12523014.

References

Cordeiro N, Gouveia C, Moraes AGO, Amico SC (2011) Natural fibers characterization by inverse gas

chromatography. Carbohyd Polym 84:110–117

Fernandez M, Fragoso A, Cao R, Banos M, Ansorge-Schumacher M, Hartmeier W, Villalonga R (2004)

Functional properties and application in peptide synthesis of trypsin modified with cyclodextrin-

containing dicarboxylic acids. J Mol Catal B-Enzym 31:47–52

Filson P, Dawson-Andoh BE, Matuana L (2009) Colorimetric and vibrational spectroscopic character-

ization of weathered surfaces of wood and rigid polyvinyl chloride-wood flour composite lumber.

Wood Sci Technol 43:669–678

Freeman R, Finder T, Bahshi LL, Willner I (2009) b-cyclodextrin-modified CdSe/ZnS quantum dots for

sensing and chiroselective analysis. Nano Lett 9:2073–2076

Hamieh T, Schultz J (2002) New approach to characterise physicochemical properties of solid substrates

by inverse gas chromatography at infinite dilution I. Some new methods to determine the surface

areas of some molecules adsorbed on solid surfaces. J Chromatogr A 969:17–25

Hamieh T, Fadlallah MB, Schultz J (2002) New approach to characterise physicochemical properties of

solid substrates by inverse gas chromatography at infinite dilution III. Determination of the acid–

base properties of some solid substrates (polymers, oxides and carbon fibres): a new model.

J Chromatogr A 969:37–47

Hedges RA (1998) Industrial applications of cyclodextrins. Chem Rev 98:2035–2044

Jiang Q, Zhang HY, Liu Y (2010) Synthesis of b-cyclodextrin-modified carbon nanocrystals and their

fluorescent behavior. Chinese Sci Bull 55:2835–2839

Kamdem DP, Riedl B (1991) Characterization of wood fibers modified by phenol-formaldehyde. Colloid

Polym Sci 269:595–603

Kazemi-Najafi S, Kiaeifar A, Tajvidi M, Hamidinia E (2008) Hygroscopic thickness swelling rate of

composites from sawdust and recycled plastics. Wood Sci Technol 42:161–168

Kimura M, Kataoka S, Tsutsumi K (2000) A study on the surface free energy of modified silica fillers and

poly(ethylene terephthalate) fibers by inverse gas chromatography. Colloid Polym Sci 278:848–854

Kord B, Hemmasi AH, Ghasemi I (2011) Properties of PP/wood flour/organ modified montmorillonite

nanocomposites. Wood Sci Technol 45:111–119

Lai X, Tang W, Ng SC (2011) Novel b-cyclodextrin chiral stationary phases with different length spacers

for normal-phase high performance liquid chromatography enantioseparation. J Chromatogr A

1218:3496–3501

Martin EM (2004) Cyclodextrins and their uses: a review. Process Biochem 39:1033–1046

Rjiba N, Nardin M, Drean JY, Frydrych R (2007) A study of the surface properties of cotton fibers by

inverse gas chromatography. J Colloid Interf Sci 314:373–380

Santos JMRCA, Guthrie JT (2005a) Analysis of interactions in multicomponent polymeric systems: the

key-role of inverse gas chromatography. Mater Sci Eng, R 50:79–107

Santos JMRCA, Guthrie JT (2005b) Study of a core-shell type impact modifier by inverse gas

chromatography. J Chromatogr A 1070:147–154

Wood Sci Technol (2014) 48:195–206 205

123

Santos JMRCA, Fagelman K, Guthrie JT (2002) Characterisation of surface Lewis acid–base properties

of poly-(butylene terephthalate) by inverse gas chromatography. J Chromatogr A 969:111–118

Schultz J, Lavielle L, Martin C (1987) The role of the interface in carbon-fiber epoxy composites.

J Adhesion 23:45–60

Shi BL, Zhang QR, Jia LN, Liu Y, Li B (2007a) Surface Lewis acid–base properties of polymers

measured by inverse gas chromatography. J Chromatogr A 1149:390–393

Shi BL, Zhao S, Jia LN, Wang LL (2007b) Surface characterization of chitin by inverse gas

chromatography. Carbohyd Polym 67:398–402

Si HY, Li B, Wang T, Lin L, Xu ZW (2013) Preparation of cyclodextrin grafting wood flour and

investigation of the release characteristics of eugenol. Wood Sci Technol 47:601–613

Spinace MAS, Lambert CS, Fermoselli KKG, De Paoli MA (2009) Characterization of lignocellulosic

curaua fibres. Carbohyd Polym 77:47–53

Szetjli J (1998) Introduction and general overview of cyclodextrin chemistry. Chem Rev 98:1743–1753

Tsutsumi K, Ohsuga T (1990) Surface characterization of modified glass fibers by inverse gas

chromatography. Colloid Polym Sci 268:38–44

Vangani V, Joseph R, Rakshit AK (1995) Adsorption of 1,4 polyisoprene at solid-liquid interface. Colloid

Polym Sci 273:118–121

Wang T, Li B, Si H, Lin L (2011) Investigation on surface activity of cyclodextrins grafting cellulose

beads through phenolphthalein probe molecule. Surf Interface Anal 43:1532–1538

Wu S, Wang T, Gao Z, Xu H, Zhou B, Wang C (2008) Selective detection of uric acid in the presence of

ascorbic acid at physiological pH by using a b-cyclodextrin modified polymer of sulfanilic acid and

N-acetylaniline. Biosens Bioelectron 23:1776–1780

Yang CQ (1993) Infrared spectroscopy studies of the cyclic anhydride as the intermediate for the ester

crosslinking of cotton cellulose by polycarboxylic acids. I. Identification of the cyclic anhydride

intermediate. J Polym Sci, Part A: Polym Chem 31:1187–1193

Yang CQ, Wang X (1997) Infrared spectroscopy studies of the cyclic anhydride as the intermediate for

the ester crosslinking of cotton cellulose by polycarboxylic acids. III. Molecular weight of a

crosslinking agent. J Polym Sci A: Polym Chem 35:557–564

Yoshioka T, Hirata S, Matsumura Y, Sakanishi K (2005) Woody biomass resources and conversion in

Japan: the current situation and projections to 2010 and 2050. Biomass Bioenerg 29:336–346

Zhang G, Long W (2010) A key review on energy analysis and assessment of biomass resources for a

sustainable future. Energ Policy 38:2948–2955

Zhao S, Song JW, Wang SL (2009) Surface characterization of a series of cured polyurethane adhesives

by inverse gas chromatography and adhesion strength testing of plywood. Wood Sci Technol

43:105–112

206 Wood Sci Technol (2014) 48:195–206

123