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Binders for higher‐solids coatings. IV. Liquid–crystalline acrylic lacquers
Author(s) -
Chen DerShyang,
Jones Frank N.
Publication year - 1988
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1988.070360112
Subject(s) - mesogen , copolymer , materials science , monomer , polymer chemistry , side chain , acrylic acid , coating , acrylic resin , chemical engineering , polymer , composite material , liquid crystalline , engineering
A previously reported synthetic procedure was used to graft oligo‐ p ‐hydroxybenzoic acid (oligo‐PHBA) to COOH‐functional acrylic copolymers. Most of the products were side‐chain LC copolymers. Length of the mesogenic oligo‐PHBA groups averaged up to five aromatic rings per group. Because these long mesogenic groups have a strong tendency to form LC domains, it was possible to prepare LC side‐chain copolymers having as little as 5 mol % of mesogenic monomer. Thus this synthetic procedure provides a versatile route for exploration of the properties of LC copolymers having relatively few but especially effective mesogenic groups. The potential utility of such LC copolymers as binders for nonbake coatings was assessed. Variables studied were molecular weight and T g of the acrylic copolymer backbone, number and average length of oligo‐PHBA segments, and the presence or absence of a flexible spacer between the acrylic backbone and the PHBA segments. Optimum LC copolymers have moderate (15,000–30,000) M n , low (−10°C) backbone T g , and low (5–7.5 mol %) population of long (5 PHBA units) oligo‐PHBA units. Such copolymers have two major advantages as coatings binders: They form concentrated, stable, low‐viscosity dispersions in common solvents, a very desirable characteristic for application. Coating films have excellent adhesion to metal, and they have an extraordinary combination of hardness (H–2H) and impact resistance (> 80 in. Ib). These properties are key indicators of coating performance and indicate that LC copolymers have excellent potential for use as binders for nonbake coatings. Other properties remain to be investigated.