Chapter

Acrylic Ester Polymers

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Abstract

The nature of the R group in its formula determines the properties of each acrylic ester and the polymers it forms. Polymers of this class are distinguished by their water-clear color and stability on aging. Acrylic monomers are extremely versatile building blocks. They readily polymerize or copolymerize with a variety of other monomers. Copolymers with methacrylates, vinyl acetate, styrene, and acrylonitrile are commercially significant. Although the acrylics have a higher cost than many other monomers their unique characteristics and efficiency offset the higher cost. Acrylic ester polymers can be made to hydrolyze to poly(acrylic acid) or an acid salt and the corresponding alcohol. Two principal processes are used for the manufacture of monomeric acrylic esters: the semicatalytic Reppe process and the propylene oxidation process, the latter of which is preferred because of economy and safety. The toxicities of acrylic monomers range from moderate to slight. The vast majority of all commercially prepared acrylic polymers are copolymers of an acrylic ester monomer with one or more different monomers. Copolymerization has led to the development of many different resins for a variety of applications. Acrylic polymers are considered to be nontoxic, and are used primarily in coatings, textiles, adhesives, and paper. Keywords: marine fouling; rosin; tributyltin (TBT); TBT-free; self-polishing copolymer (SPC); foul release; silicones

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... The poly(butyl acrylate) is tack at room temperature and is able to be used as the adhesive. Table 2.1 lists the mechanical properties of acrylic polymers (Stone, 2010). The flexibility of acrylic polymers increases with increasing chain length until it reaches the threshold: poly(n-nonyl acrylate). ...
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Narrow molecular weight resins have been synthesized by a free radical polymerization process with polydispersities comparable to those that can be achieved by an anionic polymerization process. In comparison with anionic polymerization, this free radical polymerization process has the advantage of not requiring purified reagents and can be performed in the bulk, in solution or in suspension. High monomer to polymer conversions have been achieved and, under appropriate conditions, the reaction can be performed in approximately 5 hours. The reaction has been applied towards the synthesis of monomodal and multimodal polymers with well defined modalities, as well as, block copolymers in which each of the blocks has a narrow polydispersity.
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The initial rate (Rp) and number average degree of polymerization (P̄n) of methyl methacrylate at 60° with the initiator 2,2′-azobis-(isobutyronitrile) (AIN) have been determined. P̄n values for the unfractionated low-conversion polymers were obtained from intrinsic viscosities in benzene by the equation P̄n = 2.22 × 103 [n]1/0.7.6 of Schuele, Kinsinger and Fox. The data yield the relations Rp = 3.04 × 10-3 (AIN)1/2 moles 1-1 s ec.-1 and 1/P̄n = 2.97 × 10-3 (AIN)l/2 + 0.7 × 1Q-. The monomer transfer constant is thus 0.7 × 10-5, in good agreement with the value reported by Baysal and Tobolsky. Taking 8.8 × 10-4 sec.-1 as the decomposition rate constant of AIN, the present results are compatible with an initiator efficiency of about 50% and a termination reaction which is predominantly disproportionation. On this basis, new values are suggested for the propagation and termination rate constants at 60° Chain transfer constants for two aromatic and five aliphatic thiols were determined from p̄n measurements. The greater transfer activity of the aromatic thiols is attributed to a resonance stabilization of the corresponding sulfenyl radicals. Electron-withdrawing substituents have little or no effect on the transfer activity of primary aliphatic thiols. Substitution of methyl groups on the α-carbon atom of the thiol leads to decreasing transfer activity, probably because of increased steric hindrance.
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The application of two different models to explain the steric course of asymmetric induction has been investigated in systems where each model predicts a different result. In syntheses of 2,3-diphenyl-2,3-butanediol and its monomethyl ether from various ketones, an asymmetric center is created in the presence of one already in the molecule. With systems of this type, rigid model II rather then open-chain model I predicts the configuration of the predominant product. Models are proposed which rationalize the formation of isotactic and syndiotactic polymers.
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The propagation and termination rate constants for methyl acrylate polymerization have been measured by the rotating sector method. With this monomer, under our experimental conditions, the increasing viscosity of the system causes chain termination to become diffusion-controlled even in the initial stages of polymerization. As a result, the rate of polymerization accelerates essentially at the beginning of the reaction. The rate constants for methyl acrylate have been compared with the results of Melville and Bickel on butyl acrylate, and also with the data previously obtained on methyl methacrylate, vinyl acetate and styrene. The comparison shows that, for vinyl polymerization, the frequency factors in chain propagation are low but in chain termination are nearly normal, and that the activation energies for propagation are 6-8 kilocalories, while the values for the termination reaction are somewhat lower, but not zero.