Acrylonitrile–acrylic acids copolymers. I. Synthesis and characterization

Abstract

SYNOPSISAcrylonitrile ( A N ) was copolymerized with acrylic acid ( AA) , methacrylic acid ( M A A ) , and itaconic acid (IA) by the aqueous suspension method at 40°C with ammonium persulfate and sodium metabisulfite as the redox initiator. The reactivity ratios for the AN-AA and AN-IA systems were also calculated by the Finemann-Ross and the Kelen-Tud6s methods. Higher r2 (AA) for the AN-AA system in comparison to r2 ( I A ) for the AN-IA system indicates greater reactivity of AA toward the propagating species. The influence of comonomers on intrinsic viscosity, tacticity, and number-average sequence lengths was studied. 13C-NMR spectra revealed that A N copolymers having approximately 2 mol % of AA have a greater percentage (> 30% ) of isotactic content than of homopolyacrylonitrile. Tacticity has also been calculated from infrared spectra of the polymers using stereospecific absorption bands at 1250 and 1230 cm-' . 0 1993 John Wiley & Sons, Inc. INTRODUCTIONPolyacrylonitrile ( PAN ) is modified to improve its properties by incorporation of suitable comonomers ' during polymerization. Modification of PAN by acidic comonomers increases its hydrophilicity2 and helps in the cyclization of nitrile groups during heat treatment for thermal stabilization of acrylic fib e r~.~~~ Therefore, the incorporation of certain acidic comonomers is prevalent in the synthesis of the copolymers used for the manufacture of special acrylic fibres (SAF) and as precursors of carbon fiber^.^ The copolymerization of acrylonitrile (AN) with some acidic comonomers, viz., acrylic acid and itaconic acid, along with a third monomer is reported in the patent literat~re.',~ AN may be polymerized with a number of comonomers by various methods such as solution, emulsion, aqueous suspension, and solvent water suspension p~lymerization.~ Studies reported on the polymerization of PAN homopolymer include various aspects such as ( i ) the effect of the method of polymerization on properties of the * To whom correspondence should be addressed.Journal of Applied Polymer Science, Vol. 49, 823-833 (1993) 0 1993 John Wiley & Sons, Inc.CCC OOZl-8995/93/050823-11 polymer' and (ii) the effect of the various initiat o r~.~-"For aqueous suspension polymerization, three loci of polymerization have been reported by Peebles.12 Since AN is partly soluble in water, a twophase liquid system can exist, in which one phase would be a monomer-rich phase, while the other is a monomer-poor phase. The distribution of comonomers between these two liquid phases would influence the course of polymerization. Initiation and some propagation would occur in the aqueous phase prior to the precipitation of the growing radical. The second locus of polymerization occurs at the particle-solution interphase known as the surface polymerization. The third loci of polymerization would be interior polymerization through buried free radicals, which is controlled by the diffusion of monomer to the active site. However, interior polymerization becomes less important as the polymerization t...

Effect of an acidic comonomer on thermooxidative stabilization of polyacrylonitrile

“…Details of the polymerization process are described el~ewhere.~' The copolymer P ( AN-IA) was prepared by using 5% by weight of comonomer in the initial feed, and the mole fraction of the comonomer in the final product, determined by Perkin-Elmer 240C elemental analyzer, was 2.5 mol %, which was smaller than the predicted value. 30 Intrinsic viscosities of the sample in N : N-dimethylformamide at 25°C were 2.87 and 2.58 dL/g for the homopolymer and the copolymer, respectively.…”

Copolymerization of acrylonitrile with methyl vinyl ketone

“…It is important to select a suitable technique and to optimize the conditions of polymerization for the synthesis of an acrylic polymer that satisfies the requirements for high-tenacity acrylic fibers. 2,3 Several polymerization techniques have been successfully used to synthesize homopolymers and copolymers of acrylonitrile (AN) for high-tenacity fibers. Solution, aqueous suspension, and solvent-water suspension are the most common useful techniques.…”

Rheological kinetics of acrylonitrile–acrylamide copolymer solutions in dimethyl formamide

“…The details of the polymerization technology are given elsewhere. 6,7 For comparison, ordinary AN-AM copolymer synthesized by DMF solution polymerization 8 technology was also used. Characteristics of copolymers are given in Table I.…”