Polymer/liquid dispersion, composite film and method for producing same

• US 6,319,424 B1
• Filed: 03/02/1999
• Issued: 11/20/2001
• Est. Priority Date: 10/28/1998
• Status: Expired due to Fees

• Current Assignee: Korea Research Institute of Chemical Technology
• Original Assignee: Korea Research Institute of Chemical Technology
• Inventors: Kim, Mun-Han, Park, Soo-Jin, Lee, Jae-Rock
• Primary Examiner(s): WU, SHEAN CHIU
• Application Number:
  US09/260,019
• Time in Patent Office: 994 Days
• Field of Search: 428/1.1, 252/299.01, 252/299.5, 349/10, 349/86
• US Class Current: 252/299.01
• CPC Class Codes: C09K 19/542 Macromolecular compounds
• CPC Class Codes: C09K 19/544 as dispersing or encapsulating medium around the liquid crystal

Abstract

A polymer/liquid crystal dispersion includes a liquid crystal, a surfactant and a water soluble copolymer obtained by polymerizing a hydrophilic monomer with one or more hydrophobic monomers. The concentration of the hydrophobic monomer may be 14 to 25% by weight based on the combined weight of the hydrophobic monomer and the hydrophilic monomer. The hydrophobic monomer may be styrene, 3-(trifluoromethyl)styrene, nonylphenol, methacryloyl chloride, methacrylate, and acrylate. The hydrophilic monomer may be acrylamide, acrylonitrile or acryloyl chloride. Preferably, the hydrophilic monomer is acrylamide or a derivative thereof and the hydrophobic monomer is styrene, methyl methacrylate or vinyl acetate. The liquid crystal may be a nematic liquid crystal formed of an azomethine compound or an azo compound. The water soluble copolymer, the liquid crystal, the surfactant and water may form a liquid crystal/aqueous polymer solution. In this case, the concentration of the liquid crystal in the liquid crystal/aqueous polymer solution is preferably in the range of 50 to 70% by weight and the concentration of the surfactant is preferably in the range of 1 to 5.5% by weight. A composite film may be formed from the polymer/liquid crystal dispersion and a pair of plates sandwiching the polymer liquid crystal emulsion.

Claims

1. A polymer/liquid crystal dispersion comprising:

a water soluble copolymer obtained by polymerizing a hydrophilic monomer selected from the group consisting of acrylamide, acrylonitrile and acryloyl chloride with one or more hydrophobic monomers selected from the group consisting of styrene, 3-(trifluoromethyl)styrene and nonylphenyl methacrylate, the content of the one or more hydrophobic monomers being 14 to 25% by weight based on the combined weight of the one or more hydrophobic monomers and the hydrophilic monomer;

a surfactant;

a liquid crystal; and

water,

the water soluble copolymer, the surfactant, the liquid crystal and the water forming a liquid crystal/aqueous polymer solution, the concentration of the surfactant in the liquid crystal/aqueous polymer solution being in the range of 1 to 5.5% by weight.

2. A polymer/liquid crystal dispersion according to claim 1, wherein said liquid crystal is a nematic liquid crystal formed of an azomethine compound or an azo compound.

3. A polymer/liquid crystal dispersion according to claim 1, wherein the concentration of the liquid crystal in the liquid crystal/aqueous polymer solution is in the range of 50 to 70% by weight.

4. A polymer/liquid crystal dispersion according to claim 1, wherein the surfactant is a non-ionic surfactant.

5. A sandwiched composite film, comprising:

a polymer/liquid crystal dispersion having;

a water soluble copolymer obtained by polymerizing a hydrophilic monomer selected from the group consisting of acrylamide, acrylonitrile and acryloyl chloride with one or more hydrophobic monomers selected from the group consisting of styrene, 3-(trifluoromethyl)styrene and nonylphenyl methacrylate, the content of the one or more hydrophobic monomers being 14 to 25% by weight based on the combined weight of the one or more hydrophobic monomers and the hydrophilic monomer;

a surfactant;

a liquid crystal; and

water, the water soluble copolymer, the surfactant, the liquid crystal and the water forming a liquid crystal/aqueous polymer solution, the concentration of the surfactant in the liquid crystal/aqueous polymer solution being in the range of 1 to 5.5% by weight,

a pair of plates sandwiching the polymer/liquid crystal dispersion.

6. A sandwiched composite film according to claim 5, wherein the thickness of the composite film is 6 to 25 μ

m.

7. A sandwiched composite film according to claim 5, wherein said liquid crystal is a nematic liquid crystal formed of an azomethine compound or an azo compound.

8. A sandwiched composite film according to claim 5, wherein the concentration of the liquid crystal in the liquid crystal/aqueous polymer solution is in the range of 50 to 70% by weight.

9. A sandwiched composite film according to claim 5, wherein the surfactant is a non-ionic surfactant.

10. A method for producing a polymer/liquid crystal dispersion composite film, comprising the following steps:

a) polymerizing a hydrophilic monomer selected from the group consisting of acrylamide, acrylonitrile and acryloyl chloride with one or more hydrophobic monomers selected from the group consisting of styrene, 3-(trifluoromethyl)styrene and nonylphenyl methacrylate to form a water soluble copolymer, the content of the one or more hydrophobic monomers being 14 to 25% by weight based on the combined weight of the one or more hydrophobic monomers and the hydrophilic monomer;

b) washing and drying the water soluble copolymer and then dissolving the water soluble copolymer in water and a surfactant to form a solution;

c) after steps (a) and (b), dispersing a liquid crystal into the solution to produce a liquid crystal/polymer aqueous solution, the concentration of the surfactant in the liquid crystal/aqueous polymer solution being in the range of 1 to 5.5% by weight; and

d) placing the liquid crystal/polymer aqueous solution between glass substrates in order to remove water therefrom.

11. A method for producing a polymer/liquid crystal dispersion composite film according to claim 10, wherein said liquid crystal is a nematic liquid crystal formed of an azomethine compound or an azo compound.

12. A method for producing a polymer/liquid crystal dispersion composite film according to claim 10, wherein the concentration of the liquid crystal in the liquid crystal/aqueous polymer solution is in the range of 50 to 70% by weight.

13. A method for producing a polymer/liquid crystal dispersion composite film according to claim 10, wherein the surfactant is a non-ionic surfactant.