JP2011069725A - Method for measuring functional group - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for widely and correctly measuring a functional group present on the surface of a solid material without using a complicated waveform separation. <P>SOLUTION: The method for measuring the functional group is provided with the process (a) for preparing a plurality of evaluation samples comprising a carbonaceous film, the process (b) for preparing a plurality of labeling reagents having reaction rates to each functional group which are previously measured, the process (b) for causing the evaluation samples and the labeling reagents to react to each other; the process (c) for measuring the introduction quantity of the labeling reagent introduced on a surface of each evaluation sample by using an X-ray photoelectron spectroscopy measurement method after the process (b), and the process (d) for calculating the quantity of each functional group existing on a surface of the carbonaceous film based on G=R<SP>-1</SP>Q. G is a matrix indicating the quantity of each functional group. R is a matrix indicating the reaction rate of each labeling reagent to each functional group. Q is a matrix indicating the introduction quantity of each labeling reagent. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for measuring a functional group, and more particularly to a method for measuring a functional group present on the surface of a solid material.

  A diamond-like thin film (DLC film) has a flat surface with high strength and low friction. For this reason, it is used for protection of surfaces of tools, molds, hard disks and the like. It is also used for coating the surface of medical devices that make contact with blood, such as stents and catheters, taking advantage of its smooth properties. It has been studied to improve biocompatibility by introducing functional groups such as carboxyl groups and amino groups on the surface of the DLC film. It is known that the biocompatibility of a DLC film is greatly affected by the type and amount of functional groups present on the surface. For this reason, it is required to accurately measure the type and amount of functional groups present on the surface of the DLC film.

  The type and amount of functional groups present on the surface of a carbonaceous film such as a DLC film are roughly estimated by measuring the elements present on the surface and the bonding state of these elements by X-ray photoelectron spectroscopy (XPS). can do. For example, if it can be confirmed that the carbon 1s (C1s) peak obtained by XPS measurement contains a CO—O bond component in addition to the C—C bond component, the presence of a carboxyl group (COOH) can be estimated. Also, the amount can be estimated to some extent by performing peak waveform separation. However, the waveform separation operation is complicated and the accuracy is not high. Furthermore, no information about the details of the functional groups can be obtained and COOH cannot be distinguished from esters (COO-R). Since COOH, carbonyl group (C = O), and hydroxyl group (C-OH) have peak positions, theoretically, it is possible to separate and quantify peaks by waveform separation. However, in actuality, peak separation is a function analysis with many parameters and is difficult.

  In XPS measurement, there is a chemical modification method as a method of measuring by distinguishing functional groups (for example, see Non-Patent Document 1). The chemical modification method is a method of measuring a labeling reagent by modifying the functional group using a labeling reagent that specifically reacts with a specific functional group. For example, if a labeling reagent that reacts with COOH but does not react with other functional groups and contains fluorine (F) is used, the amount of COOH can be measured by measuring the amount of F.

Y. Nakayama, et al., "J. Polym. Sci., Part A: Polym. Chem.", 1988, 26, p559

  However, few ideal compounds are known that can react specifically with a specific functional group and can be easily measured by XPS and used as a labeling reagent. For this reason, the functional group which can be measured by the conventional chemical modification method is limited. In addition, since side reactions occur almost without exception in chemical reactions, the labeling reagent may also react with functional groups that are not targeted. However, side reactions have been ignored in conventional chemical modification methods. For this reason, it cannot be said that the measurement accuracy is sufficient.

  Similar problems arise when measuring functional groups using XPS on the surface of a solid material other than the carbonaceous film.

  An object of the present application is to make it possible to measure a functional group present on the surface of a solid material more widely and more accurately without using complicated waveform separation.

  In order to achieve the above object, the present invention provides a functional group measurement method by introducing the same number of labeling reagents as the number of functional groups and solving a matrix equation using the amount of labeling reagent introduced and the reaction rate as parameters. It is set as the structure which calculates the quantity of group.

Specifically, the method for measuring a functional group according to the present invention is a method for measuring a plurality of functional groups present on the surface of a solid material, and preparing a plurality of samples for evaluation made of a solid material ( a), a step (b) of preparing a plurality of labeling reagents whose reaction rates with respect to each functional group are measured in advance, a step (b) of reacting the sample for evaluation and the labeling reagent, and a step (b) Later, in step (c), the amount of the labeling reagent introduced on the surface of each sample for evaluation is measured by X-ray photoelectron spectroscopy, and the amount of each functional group present on the surface of the solid material is determined as G Step (d) of calculating based on = R ⁻¹ Q. However, G, R, and Q are as follows, Fn (n is an integer greater than or equal to 2) is an nth functional group among a plurality of functional groups, and Lm (m is an integer greater than or equal to 2 and m = n) is the m-th labeling reagent among a plurality of labeling reagents, G _Fn is the amount of Fn present on the surface of the carbonaceous film, and Q _Lm is the introduction of Lm introduced on the surface of the carbonaceous film. R _{Lm / Fn} is the reaction rate between Lm and Fn.

  The functional group measurement method of the present invention uses the introduction amount of the labeling reagent introduced into each of the evaluation samples and the reaction rate for each functional group of the labeling reagent measured in advance. Calculate the amount of For this reason, since the side reaction of the labeling reagent is not ignored, the amount of the functional group can be measured more accurately. In addition, it is not necessary to use a labeling reagent that reacts only with a specific functional group in consideration of side reactions. Accordingly, the selection of the labeling reagent is facilitated, and it is possible to easily cope with various functional groups.

  In the functional group measurement method of the present invention, each of the labeling reagents contains a hetero element, and in the step (c), the amount of the labeling reagent introduced may be measured by measuring the amount of the hetero element.

  In the functional group measurement method of the present invention, the plurality of functional groups are a hydroxyl group, a carbonyl group, and a carboxyl group, and the plurality of labeling reagents are trifluoroacetic acid, hydrazine, and a mixture of trifluoroethanol and diisopropylcarbodiimide. Good.

  In the method for measuring a functional group of the present invention, the step (b) may be a gas phase reaction.

  In the functional group measurement method of the present invention, the reaction rate for each functional group may be determined by reacting a reference polymer film having a single functional group with each labeled compound.

  In the functional group measurement method of the present invention, the solid material may be a carbonaceous film.

  According to the functional group measurement method of the present invention, the functional groups present on the surface of the solid material can be measured more widely and more accurately without using complicated waveform separation.

(A) And (b) is a schematic diagram which shows reaction of a functional group and a labeling reagent, (a) shows an ideal reaction, (b) has shown the case where a side reaction arises. It is a reaction scheme which shows the labeling reaction of a hydroxyl group. It is a reaction scheme which shows the labeling reaction of a carbonyl group. It is a reaction scheme which shows the labeling reaction of a carboxyl group. It is a figure which shows the chamber for gas phase reaction used in the 1st Example. It is a chart which shows the XPS measurement result of the sample for evaluation after making it react with each labeling reagent in the 1st example.

In this specification, the carbonaceous film is a film containing sp ² carbon-carbon bonds (graphite bonds) and sp ³ carbon-carbon bonds (diamond bonds) represented by diamond-like films (DLC films). It may be an amorphous film such as a DLC film or a crystalline film such as a diamond film.

  First, the principle of measuring the amount of functional groups present on the surface of a solid material will be described. In the following, a carbonaceous film will be described as an example of the solid material, but the functional group can be measured in the same manner for solid materials other than the carbonaceous film.

  First, consider a case where a carbonaceous film 101 having a functional group F1 and a functional group F2 on the surface is reacted with a labeling reagent L1 as shown in FIG. The functional group F1 and the functional group F2 are functional groups that are difficult to distinguish by X-ray photoelectron spectroscopy (XPS) measurement. The labeling reagent L1 is a reagent that specifically reacts with the functional group F1.

  When the reaction between the carbonaceous film 101 and the labeling reagent L1 proceeds ideally, as shown in FIG. 1A, all the functional groups F1 are labeled with the labeling reagent L1 to become F1L1. Accordingly, assuming the amount of the labeling reagent L1 introduced on the surface of the carbonaceous film 101, the amount of the functional group F1 can be measured. If the labeling reagent L1 contains a specific heteroelement that is hardly contained in the carbonaceous film 101, the amount of the labeling reagent L1 introduced on the surface of the carbonaceous film 101 can be easily measured. .

However, in practice, as shown in FIG. 1B, the reaction rate R _{L1 / F1} between the labeling reagent L1 and the functional group F1 is usually not 100%. Further, a side reaction in which F2L1 is generated by the reaction between the labeling reagent L1 and the functional group F2 occurs. For this reason, the introduction amount Q _L1 of the labeling reagent L1 introduced on the surface of the carbonaceous film 101 is not the amount of the functional group A but the abundance amount G _F1 of the functional group _F1 and the reaction rate R _{L1 / F1} . although it multiplied by the abundance G _F2 of objects and a functional group F2 and reaction rate R _{L1 / F2} becomes the sum. That is, the relationship shown in the following formula (1) is established.

Q _L1 = R _{L1 / F1} G _F2 + R _{L1 / F2} G _F2 (1)
Further, when there are n types (n is an integer of 2 or more) of functional groups on the surface of the carbonaceous film 101, m types (m is an integer of 2 or more and m = n) are reacted with the labeling reagent. Consider the case. In this case, since m and n are equal, the amount G of the functional group and the introduction amount Q of the labeling reagent are an n-column matrix, R is an n-order square matrix, and a matrix as shown in the following equation (2) The equation holds.

Therefore, by using the inverse matrix R ⁻¹ , the target functional group amount G can be obtained as shown in the equation (3).

G = R ⁻¹ Q (3)
The reaction rate R _{Lm / Fn} between the labeling reagent Lm and the functional group Fn can be experimentally determined by reacting the labeling reagent Lm with a reference polymer film having only the functional group Fn. For example, if polyvinyl alcohol is used as the reference polymer film, the reaction rate between the labeling reagent and the hydroxyl group (C—OH) can be determined. If polyacrylic acid is used, the reaction rate with a carboxyl group (COOH) can be obtained, and if polyvinyl methyl ketone is used, the reaction rate with a carbonyl group (C = O) can be obtained. Similarly, if polyallylamine is used, the reaction rate with an amino group can be obtained, and if polyethyl methacrylate or polyvinyl acetate is used, the reaction rate with an ester group can be obtained.

  In addition, since the side reaction is taken into consideration, the labeling reagent Lm does not necessarily need to specifically react only with the functional group Fn. Even in the case of a labeling reagent that reacts with a plurality of functional groups, it is sufficient that the reaction rate for each functional group is clear. For this reason, the advantage that selection of a labeling reagent becomes easy is also acquired. If each labeling reagent has a hetero element not contained in the carbonaceous film, the amount introduced can be easily measured by XPS measurement. Since an ordinary carbonaceous film is substantially composed of carbon and hydrogen, the amount introduced can be easily measured if it contains a heteroelement such as fluorine (F) or nitrogen (N). When fluorine (F) or silicon (Si) is introduced into the carbonaceous film for the modification of the carbonaceous film, a labeling reagent containing an element other than these elements may be used. However, even if it is a labeling reagent containing the hetero element contained in the carbonaceous film, the introduction amount can be obtained by taking the difference. Further, since each labeling reagent is reacted independently for measurement, a plurality of labeling reagents may contain the same heteroelement. Furthermore, the reaction between the labeling reagent and the functional group need not be completed in one step, and may be a multi-step reaction.

  The combination of the labeling reagents is not particularly limited. When C—OH, C═O, and COOH are measured, trifluoroacetic anhydride (TFAA), hydrazine (Hyd), trifluoroethanol (TFE), and diisopropylcarbodiimide are used. A combination with (DIC) may be used.

When trifluoroacetic anhydride (TFAA) reacts with C—OH, COCF ₃ is introduced as shown in FIG. For this reason, when the carbonaceous film before the reaction does not contain fluorine, the introduction amount Q _{TFAA of} TFAA relative to the total carbon amount can be expressed as shown in the formula (4).

[COCF ₃ ] is the number of atoms of COCF ₃ , and [C] _All is the number of atoms of all carbons. [F] is the number of fluorine atoms determined by XPS measurement, and [C] is the number of carbon atoms determined by XPS measurement. In XPS measurement, [C] can be obtained by dividing the area of the C1s peak by the sensitivity coefficient. [F] can be obtained by dividing the area of the F1s peak by the sensitivity coefficient.

Similarly, the reaction of hydrazine (Hyd) with C═O proceeds as shown in FIG. In this case, the Hyd introduction amount Q _{Hyd with} respect to the total carbon amount can be expressed as shown in Equation (5). However, [N] is the number of nitrogen atoms determined by XPS measurement.

Similarly, the reaction of trifluoroethanol (TFE) and diisopropylcarbodiimide (DIC) with COOH proceeds as shown in FIG. In this case, the introduction amount Q _{TFE / DIC} of TFE and DIC with respect to the total carbon amount can be expressed as shown in Equation (6).

In the method for measuring a functional group on the surface of the solid material of the present disclosure, it is not always necessary to use a labeling reagent having high specificity that reacts only with a specific functional group. Moreover, each labeling reagent may contain the same heteroelement. It is preferable that the hetero element contained in the labeling reagent is hardly contained in the solid material itself and is easily quantified by XPS measurement. Further, if the amount introduced by taking a difference or the like can be accurately quantified, there is no problem even if it is contained in the solid material itself. Therefore, for example, the labeling reagent may contain a heteroelement such as fluorine (F), chlorine (Cl), nitrogen (N), titanium (Ti), sodium (Na), or sulfur (S). Specifically, heptafluorobutyryl chloride (HFBC0) or C ₆ F ₅ NHO mainly reacting with an amino group, CF ₃ CO—Cl, ClC ₆ H ₄ —NCO or diisopropoxy titanium mainly reacting with a hydroxyl group _{bisacetylacetonate, C 6 F 5 NH = NH} 2 or ClC ₆ H ₄ NH = NH ₂ mainly reacts with a carbonyl group, sodium hydroxide primarily reacts with a carboxyl group, nitrate or tloc ₂ H ₅ and peroxide Sulfur dioxide or the like that mainly reacts with the group can also be used as a labeling reagent.

  Below, the measuring method of the functional group on the surface of a solid material is demonstrated still in detail using an Example. In the following, an example using a carbonaceous film as a solid material will be described. However, an inorganic material film such as a metal film other than a carbonaceous film and an organic material film such as a polymer material film also exist on the surface in the same manner. The functional group to be measured can be measured.

(First embodiment)
First, a DLC film was formed on the surface of the substrate using a known ionized vapor deposition method, and an evaluation sample was formed. Next, the labeling reagent was reacted with the sample for evaluation under the conditions shown in Table 1, respectively.

  Table 2 shows the reaction rate R between the labeling reagent and the functional group obtained by reacting each labeling reagent with the reference polymer film. Polyvinyl alcohol is used for the reference polymer film having only C—OH, polyvinyl methyl ketone is used for the reference polymer film having only C═O, and polyacrylic acid is used for the reference polymer film having only COOH. It was.

  The sample for evaluation and the labeling reagent were reacted by a gas phase method using a chamber as shown in FIG. Next, XPS measurement was performed on each sample for evaluation reacted with the labeling reagent. In the XPS measurement, the X-ray incident angle and intensity were adjusted to measure about 0.3 nm from the sample surface. The measurement result of each evaluation sample is shown in FIG.

When the functional group concentration (mol%) with respect to the total carbon amount of C—OH, C═O and COOH was determined using the result obtained by XPS measurement and the formula (3), G _C—OH was detected. G _{C = O} was 23% and G _COOH was 4%.

(Second embodiment)
After forming the DLC film on the surface of the substrate, the DLC film was wet-oxidized to prepare an evaluation sample. Wet oxidation was performed by immersing the DLC film for 10 minutes in a 1 to 3 mixed solution of 30% hydrogen peroxide and concentrated sulfuric acid. Other conditions were the same as in the first example, and C—OH, C═O and COOH on the surface of the DLC film were measured. G _C-OH was not detected, G _{C = O} was 44%, and G _COOH was 7%.

  The method for measuring a functional group according to the present invention can measure the functional group existing on the surface of the solid material more widely and more accurately without using complicated waveform separation, and the characteristics of the solid material including the carbonaceous film. Useful for evaluation.

Claims (6)

A method for measuring the amount of a plurality of functional groups present on the surface of a solid material,
Preparing a plurality of evaluation samples made of the solid material (a);
A step (b) of preparing a plurality of labeling reagents whose reaction rates with respect to the respective functional groups are measured in advance;
A step (b) of reacting the sample for evaluation and the labeling reagent, respectively;
After the step (b), a step (c) of measuring the amount of the labeling reagent introduced to the surface of each of the evaluation samples by X-ray photoelectron spectroscopy;
And a step (d) of calculating the amount of each functional group present on the surface of the solid material based on the following formula:
G = R ^-1 Q
However,

Fn (n is an integer of 2 or more) is the n-th functional group of the plurality of functional groups, and Lm (m is an integer of 2 or more and m = n) is the labeling reagent. G _Fn is the amount of Fn present on the surface of the carbonaceous film, Q _Lm is the amount of _Lm introduced on the surface of the carbonaceous film, R F _{Lm / Fn} is the reaction rate between Lm and Fn. Each of the labeling reagents includes a heteroelement,
The method for measuring a functional group according to claim 1, wherein in the step (c), the introduction amount of the labeling reagent is measured by measuring the amount of the hetero element. The plurality of functional groups are a hydroxyl group, a carbonyl group, and a carboxyl group,
The method for measuring a functional group according to claim 1 or 2, wherein the plurality of labeling reagents are trifluoroacetic acid, hydrazine, and a mixture of trifluoroethanol and diisopropylcarbodiimide.   The method for measuring a functional group according to claim 1, wherein the step (b) is a gas phase reaction.   The reaction rate with respect to each said functional group is calculated | required by making the reference | standard polymer film which has a single functional group, and each said label | marker compound react, It is any one of Claims 1-4 characterized by the above-mentioned. Functional group measurement method.   The method for measuring a functional group according to claim 1, wherein the solid material is a carbonaceous film.

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