V. Sreenivasulu Reddy

Polymers derived from 2-phenyl-1,1,1,3,3,3-hexafluoropropan-2-ol and its derivatives

Abstract Over the past 25 yr several classes of polymers (epoxy resins, polyurethanes, polyacrylates etc.) derived from aromatic monomers bearing —C(CF 3 ) 2 OH groups have been developed. These materials have exceptional heat, light and chemical resistance in addition to low surface energy, low water absorption and low dielectric constant. They have been suggested for use in a variety of ways such as biological anti-fouling materials, dental composites, cladding for optical fibers, textile impregnants and marine coatings.

Synthesis and characterization of new silicon-containing fluoroacrylate monomers and polymers: 3☆

Abstract A series of new silicon-containing fluoroacrylate polymers and copolymers (with methyl acrylate) has been prepared, starting from 1,3-bis(hexafluoro-2-hydroxy-2-propyl)benzene (1,3-HFAB). The fluorinated, silicon-containing alcohol precursor was synthesized in two steps by reacting 1,3-HFAB first with n-butyl lithium and subsequently with dichlorodimethylsilane. The silicon-containing alcohol was finally reacted with acryloyl or methacryloyl chloride to give the corresponding monomers. Polymers were obtained by bulk free radical polymerization using α,α′-azobisisobutyronitrile as initiator. The polymers, which have inherent viscosities ranging from 0.20 to 0.33 dl g−1, form brittle hydrophobic films by solution casting. The polyacrylates are stable to about 375°C (10% weight loss) in nitrogen and exhibit glass transition from 67 to 110°C.

Polymers from 2,5-difluoroterephthalic acid. I. Polyesters

A new synthetic route to 2,5-difluoroterephthalic acid (DFTA) was devised and from this several new series of polymers were prepared by polycondensation. This inaugural paper will cover polyesters while subsequent papers will report on keto polyethers, polyamides and other backbones derived from DFTA. DFTA was synthesized from 2,5-difluorotoluene, which was acylated and subsequently converted to the diacid by a several step oxidation process. Various polyesters were prepared by reacting it with numerous bisphenols and diols by solution condensation to give a series of difluoroterephthalate polyesters with viscosities ranging from 0.16 to 0.61 dl/g. Thermogravimetric analyses showed that the polyesters had thermal stabilities up to 480°C in nitrogen; melting temperatures ranged from 127 to 318°C.

Synthesis and characterization of new fluorinated polyacrylates: 2

A series of new fluorinated acrylate polymers and copolymers (with methyl acrylate and methyl methacrylate) has been prepared starting from 1,3-bis(hexafluoro-2-hydroxy-2-propyl)benzene (1,3-HFAB). 1,3-HFAB was first reacted with dimethylsulfate in the presence of aqueous sodium hydroxide to yield 1-(hexafluoro-2-hydroxy-2-propyl)-3-(hexafluoro-2-methoxy-2-propyl)benzene which was reacted with acryloyl or methacryloyl chloride to give the corresponding fluorinated acrylate or methacrylate monomers. The polymers were obtained by bulk or solution free radical polymerization techniques with α,α′-azobisisobutyronitrile as initiator. The polymers had viscosities ranging from 0.21–0.41 dl g−1, and the polyacrylates formed brittle films by solution casting. Thermogravimetric analysis showed that they had thermal stability up to 391°C in nitrogen and glass transition temperatures from 50 to 104°C.

Synthesis and Characterization of New Diisocyanate-Based Polyurethane Cationomers

Abstract New diisocyanates, which contain tertiary nitrogen, have been prepared and used in the preparation of polyurethane cationomers. The ionomers were synthesized from commercial diisocyanates (toluene diisocyanate or hexamethylene diisocyanate) as well as from new diisocyanates [N,N′-bis(m- or p-isocyanato-phenyl)pyromellitic diimide] with polypropylene glycol, chain extended with 1,4-butanediol and/or N-methyldiethanolamine and then quaternized with 1,4-bis(chloromethyl)benzene. The cationomers thus formed were characterized by thermogravimetric analysis and differential scanning calorimetric measurements.

Polyacrylates containing hexafluoroisopropoxy pendant functions

Abstract A series of new polyacrylates was synthesized by incorporating the hexafluoroisopropoxy unit pendant to the backbone. The fluorinated monomers were synthesized by reacting 4-fluoro(2-hydroxyhexafluoroisopropyl)benzene with acrylic or methacrylic acid chlorides. The polymers were obtained by bulk, free-radical polymerization techniques using α,α′-azobisisobutyronitrile as initiator. The polymers had viscosities ranging from 0.15 to 1.41 dl g −1 and had good film-forming properties. Thermogravimetric analysis showed that they had thermal stability up to 370°C in N 2 ; glass transition temperatures were in the range 64 to 119°C.

Synthesis of a New Diisocyanate-Based Polyurethane

Abstract A new polyurethane was prepared by polycondensation reaction of the α, 4-diisocyanate anisole with polypropylene glycol. Synthetic procedures for the preparation of the new diisocyanate are described. The monomers and the polymers formed therefrom are characterized by IR and NMR spectral data. Thermal stability of the polymer was studied by thermogravimetry.

Polyacrylates Containing the Hexafluoroisopropylidene Function in the Pendant Groups

New acrylic monomers containing the hexafluoroisopropylidene function in the pendant group have been synthesized, and their homopolymerization or copolymerization with nonfluorinated acryclic comonomers was performed by free-radical bulk techniques. Colorless, transparent films were cast from polymer solutions. The inclusion of a hexafluoroisopropylidene group in these polymers led to increased thermal stability and increased Tg. When the pendant group containing 6F also had some methylene units the thermal stability of the corresponding polymers and copolymers was influenced predominantly by these aliphatic groups rather than by the 6F groups. Fluorinated homopolymers showed no water absorption as measured to the nearest 0.1 wt%. Additional properties of these polymers are under investigation.

Hexafluoroisopropoxy-containing polyesters

Abstract A series of new polyesters containing the hexafluoro-2-propoxy group was synthesized by solution polycondensation. The 4-(2-hydroxyhexafluoro-2-propyl)benzoyl chloride was synthesized by dichromate oxidation of commercial available 4-(2-hydroxyhexafluoro-2-propyl)toluene and subsequent reaction with SOCl2. The homopolyester of this acid chloride as well as several copolyesters of 1,3- and 1,4-bis(2-hydroxyhexafluoro-2-propyl)benzene were synthesized. These highly crystalline polyesters show limited solubility in common organic solvents but are all soluble in dimethylacetamide-LiCl. Inherent viscosities ranged from 0.12 to 0.85 dl g−1. All of the polyesters showed similar thermal stabilities, exhibited weight loss in a single step and decomposed completely with negligible quantity of residue.

New Aromatic Diacids Containing the Trifluoromethyl Group and their Polyamides

A series of new fluorinated, high-temperature polymers has been prepared from 1, 1, - bis(p-carboxyphenyl)-2, 2, 2-trifluoroethanol (3FOH). This diacid was synthesized by oxidation of 1, 1-di(p-tolyl)-2, 2, 2-trifluoroethanol, which was obtained from p-bromotoluene and ethyl trifluoroacetate. The 3FOH was also reacted with dimethyl sulphate to yield 1-methoxy-1, 1- bis(p-carboxyphenyl)-2, 2, 2-trifluoroethane (3FM), and with SOCl2 to produce 1-chloro-1, 1- bis(p-chloroformylphenyl)-2, 2, 2-trifluoroethane (3FCl). These two diacids, as the acid chlorides, were polymerized with six aromatic and four aliphatic diamines to produce polyamides which had viscosities ranging from 0.32 to 1.52 dl g−1, thermal stabilities up to 518 °C in nitrogen and glass transition temperatures from 165 °C to 337 °C. The dielectric constants of these polyamides ranged from 2.64 to 2.99. The 3FM- and 3FCl-containing polyamides were compared with the 6F (hexafluoroisopropylidene) analogues and found to be somewhat less thermally stable and had equal or lower T gs.