G. N. Babu

Analysis of the stereochemistry of poly(2,3-epoxypropyl methacrylate) by 75 MHz 13C n.m.r. spectroscopy

Abstract The tacticity of poly(2,3-epoxypropyl methacrylate) has been analysed. For detailed elucidation of stereochemical features, polymers with varying degrees of tacticities were synthesized by anionic and free radical polymerization. Using two-dimensional 13C1H correlation, signal assignments to different carbon atoms have been made. Using the peak multiplicities for carbonyl carbon atom resonance, in particular, tacticity assignments up to the pentad level have been achieved. The validity of sequence assignments has been tested and confirmed by calculated values from statistical relationships. While the anionically polymerized sample in toluene obeys a first-order Markov type chain growth process, the chain propagation for free radical polymer and anionic polymer in THF has been found to be Bernoullian.

Pressure sensitive adhesives of acrylic polymers containing functional monomers

Abstract Pressure sensitive adhesives possessing good cohesive strength have been prepared by copolymerizing n-butyl acrylate with various functional monomers. The effect of the polar nature and of the concentration of comonomer on tack, adhesion and cohesion was studied. The cohesive strength of the adhesive was determined on various surfaces. A comparative study was made to assess the effectiveness of a particular comonomer on the basis of the results obtained.

Radiolysis of Resist Polymers. 1. Poly(methyl-alpha-haloacrylates) and Copolymers with Methylmethacrylate.

Methyl alpha-chloroacrylate (MCA) and methyl alpha-bromoacrylate (MBA) were copolymerized with methyl methacrylate (MMA) over a broad range of composition. The copolymers were exposed to gamma-radiation to determine chain scission susceptibility. The mechanisms of degradation of copolymers towards radiation was suggested from product analysis. The radiolysis of copolymers of MMA with MCA and MBA are dominated by the alpha-halogenated monomers.

Resist polymers: Part VIII—Thermolysis of bromine-containing acrylate polymers

Abstract The thermal stability and degradation behaviour of poly(2-bromoethyl methacrylate (PBEMA), poly(2,3-dibromopropyl methacrylate) (PDBPMA), poly(methyl-α-bromoacrylate) (PMBA) and their copolymers have been investigated by thermogravimetric analysis in nitrogen and rapid pyrolysis in helium. Both ester decomposition and main chain scission occur for the bromo methacrylate polymers, with the former playing the dominant role. On the other hand, PMBA and its copolymer yield methyl bromide as the principal product. Possible mechanisms of formation of these products are suggested and discussed in the light of the experimental evidence. The thermolysis results are compared with radiolysis results.

Resist polymers: Part VII—Thermolysis of fluoroalkyl methacrylates

Abstract Pyrolysis-GC-MS has been performed for fluoroalkyl methacrylates at 600° in He. The major products of pyrolysis are CO 2 , acetaldehyde, fluoroacetaldehyde and vinyl fluoride for poly(2-fluoroethyl methacrylate), CO 2 , vinylidene fluoride, 2,2,2-trifluoroethanol and monomer for poly(2,2,2-trifluoroethyl methacrylate) and CO 2 , 1,1,1,3,3,3-hexafluoropropane, fluoral and hexafluoro- i -propyl formate for poly(hexafluoro- i -propyl methacrylate). Furthermore, comparison of the thermolysis and previously published radiolysis results showed that they proceed via entirely different mechanisms. The results demonstrate the accessibility of multiple reaction pathways influenced by the stereoelectronic effects of the fluoroalkyl groups.

Resist polymers: Part IX—Thermolysis of chlorine-containing acrylate polymers

Abstract The thermal degradation of poly(chloroethyl methacrylate) (PCEMA), poly(trichloroethyl methacrylate) (PTCEMA), poly(methyl-α-chloroacrylate) (PMCA) and their copolymers with methyl methacrylate (MMA) has been investigated. Both ester decomposition and main chain scission occur for the chloroalkyl methacrylate polymers with the former playing the dominant role. In contradistinction, HCl elimination and aromatization prevail over other processes for PMCA. The thermolysis results are compared with radiolysis results.

Radiolysis of Resist Polymers. 2. Poly(haloalkylmethacrylates) and Copolymers with Methylmethacrylate.

Homopolymers of 2-fluoroethyl methacrylate (FEMA), 2-chloroethyl methacrylate (CEMA) 2-bromoethyl methacrylate (BEMA), 2,2,2-trichloroethyl methacrylate (TCEMA), 2,3-dibromopropyl methacrylate (DBPMA) and copolymers with MMA over a range of compositions have been synthesized. Gamma-radiolysis yields for scission (Gs), crosslinking (Gx) and radical formation (Gr) were determined. The volatile products were analyzed by GC-MS. Probable mechanisms of radiolysis of all polymers were proposed.

Pyrolysis/gas chromatography/mass spectrometry of glycidyl methacrylate—alkyl acrylate copolymers

Abstract Thermal degradation pattern of copolymers of glycidyl methacrylate with alkyl acrylates have been studied by pyrolysis/gas chromatography/mass spectrometry method. Various degradation products have been identified and based on the products obtained, the mechanisms of polymer degradation have been elucidated.

Organotin Polyimides: Structure-Property Relationship

Thermally stable materials are of great importance in a variety of applications such as adhesives for metal metal — metal bondings protective coatings, nose cones for missiles, ablative heat shields for satellites, and numerous other aero-space uses whenever ther is a need to use in extreme environmental conditions (1). Among thermally stable polymers, aromatic polyimides possess an unusual combination of mechanical, electrical, thermal and chemical properties. These properties have generally been attributed to the structural features of the polymers including the inert nature of the imide leankage and aromatic groups. Polyimides possessing silicon and phosphorus have attracted the attention of many researchers (2). A number of tin-containing polymers have been synthesized but the synthesis of tin polyimides has not yet been reported. Tin polymers, such as tributyltin (meth)acrylates and poly(tin esters) are reported to exihibit antifungal properties, antibacterial activity and are water repellents. These polymers also exhibit fiber and coating properties (3–5) as well as moderate stability (6). One of the most promising classes of devices for controlled release of active agents are erodible polymer carriers. These can be of several types. One type consists of polymeric backbones, either linear or crosslinked, with the active agents chemically attached to the backbone as pendent groups. As the linkages connecting the active agent to the polymeric carrier are eroded, eg., hydrolyzed, by environmental agents, the active agents are released, leaving the polymer backbone behind. Another type consists of the incorporation of the active agent into the polymer backbone of the polymer chain.

Preparation and Properties of 2-Hydroxypropyl Methacrylate-Alkyl Acrylate Copolymer Net-Works

Hydrogels, in the swollen state, exhibit poor mechanical properties which need to be improved to increase their utility. Polymeric materials with a wide range of physical properties suitable for a broad variety of applications can be prepared using hydrophobic monomers with a variety of crosslinkers. The polymerization of 2-hydroxyethyl methacrylate(HEMA) with ethylene glycol dimethacrylate(EGDMA) in the presence of organic peroxides gave a hydrophilic copolymer useful for coatings, mouldings and carriers for biologically active substances (1). The swelling properties of polyhydroxyalkyl acrylates in water depends to a certain extent on the degree of crosslinking, concentration of additives in the water and the amount of water used in the polymerization process. When HEMA was polymerized in aqueous solution with high water content polymer precipitates out from the monomer and yields opaque gels or porous sponges (2). Mechanical behavior of poly(HEMA) hydrogels prepared in the presence of various concentrations of crosslinking agents and diluents has been investigated. A copolymer prepared from a hydroxyalkyl (meth)acrylate, a crosslinking agent such as EGDMA and an unsaturated acid like methacrylic acid are suitable for manufacturing contact lenses (3).