Methacrylic Acid and Methyl Methacrylate Copolymer

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition
Issued and maintained by the United States Pharmacopeial Convention (USP)
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1 DEFINITION 

Methacrylic Acid and Methyl Methacrylate Copolymer consists of methacrylic acid and methyl methacrylate monomers arranged in a random distribution. Methacrylic acid units in Methacrylic Acid and Methyl Methacrylate Copolymer, previously dried, are NLT 27.6% and NMT 50.6%. It may contain suitable surface-active agents. 

2 IDENTIFICATION 

Change to read: 

2.1 A.

Spectroscopic Identification Tests 〈197〉, Infrared Spectroscopy: 197K (CN 1-May-2020) 

Use USP Methacrylic Acid and Methyl Methacrylate Copolymer (1:1) RS for Methacrylic Acid and Methyl Methacrylate Copolymer, with a range of 46.0%–50.6% for methacrylic acid units. 

Use USP Methacrylic Acid and Methyl Methacrylate Copolymer (1:2) RS for Methacrylic Acid and Methyl Methacrylate Copolymer, with a range of 27.6%–30.7% for methacrylic acid units. 

2.2 B.

It meets the requirements of the Assay. 

3 ASSAY 

3.1 Procedure 

Sample: 1 g, previously dried 

Analysis: Dissolve the Sample in 100 mL of neutralized acetone, and titrate with 0.1 N sodium hydroxide VS, determining the endpoint potentiometrically (see Titrimetry 〈541〉). Each mL of 0.1 N sodium hydroxide is equivalent to 8.609 mg of methacrylic acid (C₄H₆O₂) units.

Acceptance criteria 

Methacrylic acid and methyl methacrylate copolymer (1:2): 27.6%–30.7% 

Methacrylic acid and methyl methacrylate copolymer (1:1): 46.0%–50.6% 

4 IMPURITIES 

4.1 Residue on Ignition 〈281〉: NMT 0.1% 

4.2 Limit of Methacrylic Acid and Methyl Methacrylate 

Phosphate buffer: Prepare an aqueous solution containing 17.8 g/L of anhydrous dibasic sodium phosphate and 17.0 g/L of monobasic potassium phosphate. Adjust with phosphoric acid to a pH of 2.0. This buffer has a concentration of 0.125 M. 

Mobile phase: Add phosphoric acid dropwise to water to obtain a solution with a pH of 2.0. Prepare a mixture of this acidied water and methanol (80:20), and degas. 

Standard solution: Dissolve 0.05 g of methacrylic acid and 0.05 g of methyl methacrylate in 5 mL of butanol, and add methanol to exactly 100 mL. Transfer 1.0 mL of this solution to a 100-mL volumetric ask. Dilute with methanol to volume. Mix 3.0 mL of this solution with 10.0 mL of Phosphate buffer. This solution contains 1.15 µg/mL each of methacrylic acid and methyl methacrylate. [Note—Due to volatility of monomers, tightly closed vials should be used.] 

Sample solution: Transfer 1 g of Methacrylic Acid and Methyl Methacrylate Copolymer to a 50-mL volumetric ask, dilute with methanol to volume, and mix. Add 3 mL of this solution dropwise, while continuously stirring, to a beaker that contains 10.0 mL of Phosphate buffer. Remove the precipitated polymer to obtain a clear supernatant by centrifugation (e.g., NLT 5000 × g for NLT 5 min). Use the clear supernatant. [Note—Due to volatility of monomers, tightly closed vials should be used.] 

Chromatographic system 

(See Chromatography 〈621〉, System Suitability.) 

Mode: LC 

Detector: UV 202 nm 

Column: 4.0-mm × 12.5-cm; 7-µm packing L1 

Flow rate: 2 mL/min 

Injection volume: 20 µL 

System suitability 

Sample: Standard solution 

[Note—The relative retention times for methacrylic acid and methyl methacrylate are 1.0 and 2.8, respectively.] 

Suitability requirements 

Resolution: NLT 2.0 between methacrylic acid and methyl methacrylate 

Relative standard deviation: NMT 5.0% 

Analysis 

Samples: Standard solution and Sample solution 

Calculate the percentage of each monomer (methacrylic acid or methyl methacrylate) in the portion of Methacrylic Acid and Methyl Methacrylate Copolymer taken: 

Result = (r_u/r_s) × (C/W) × V_F × D × F × 100 

r_u = peak response of the monomer (methacrylic acid or methyl methacrylate) from the Sample solution 

r_s = peak response of the monomer (methacrylic acid or methyl methacrylate) from the Standard solution 

C = concentration of the monomer (methacrylic acid or methyl methacrylate) in the Standard solution (µg/mL) 

W = weight of Methacrylic Acid and Methyl Methacrylate Copolymer taken to prepare the Sample solution (g) 

V_F = nal volume of the Sample solution, 13 mL 

D = dilution factor for preparation of the Sample solution, 16.7 

F = conversion factor, 10−6 g/µg 

Acceptance criteria: NMT 0.05% for the total amount of monomers 

5 SPECIFIC TESTS 

5.1 Viscosity—Rotational Methods 〈912〉 

Analysis: Place 254.6 g of isopropyl alcohol and 7.9 g of water in a test ask. Add a quantity of Methacrylic Acid and Methyl Methacrylate Copolymer, equivalent to 37.5 g of solids on the dried basis, while stirring by means of a magnetic stirrer. Close the ask, and continue stirring until the polymer has dissolved completely. Adjust the temperature to 20 ± 0.1°. Equip a rotational rheometer1 following Method II. The shear rate under the test condition is NLT 1 s−1 and NMT 100 s−1. Validations demonstrate that an equivalent viscosity value is also obtained using a rotational viscometer with a cylindrical spindle 1.9 cm in diameter and 6.5 cm high, attached to a shaft 0.3 cm in diameter.2 The spindle rotates at 30 rpm at an immersion depth of 8.15 cm (see Method I). Follow the instrument manufacturer's directions to measure the apparent viscosity. 

Acceptance criteria 

Methacrylic acid and methyl methacrylate copolymer, with a range of 46.0%–50.6% for methacrylic acid units: 60–120 mPa · s Methacrylic acid and methyl methacrylate copolymer, with a range of 27.6%–30.7% for methacrylic acid units: 50–200 mPa · s 

5.2 Loss on Drying 〈731〉 

Analysis: Dry at 110° for 6 h. 

Acceptance criteria: NMT 5.0% 

6 ADDITIONAL REQUIREMENTS 

6.1 Packaging and Storage:

Preserve in tight containers, and store at controlled room temperature. 

6.2 Labeling

Label it to indicate the range of methacrylic acid units. The labeling also indicates the name and quantity of any added surface-active agent. 

6.3 USP Reference Standards 〈11〉 

USP Methacrylic Acid and Methyl Methacrylate Copolymer (1:1) RS (USP Methacrylic Acid Copolymer, Type A RS) 

USP Methacrylic Acid and Methyl Methacrylate Copolymer (1:2) RS (USP Methacrylic Acid Copolymer, Type B RS) 

1 A suitable rheometer is available from Physica Messtechnik GmbH as the Coaxial-Cylinder 27 or the Double-Gap-Cylinder 26.7, or any other equivalent rheometer. 

2 A suitable spindle is available from Brookeld as an LV1 spindle, or the equivalent.