Polymers with aldehyde and acetal groups based on esters of methacrylic acid

Soluble poly(2,2-diethoxyethyl methacrylate) (1a) was prepared by radical polymerization in solution. Copolymers from 2,2-diethoxyethyl methacrylate (3a) , 2-hydroxyethyl methacrylate (4) and ethylene dimethacrylate (5) were prepared by suspension polymerization in the form of crosslinked beads (50–220 μm in diameter, specific surface area up to 38 m²/g). Acetal groups of these polymers resist direct hydrolysis, but can be transacetalized. Soluble poly(3,3-diethoxypropyl methacrylate) (1b) was prepared by radical polymerization in solution. Copolymers with 4 and 5 were prepared by suspension polymerization in the form of crosslinked beads (30 – 140 μm in diameter; specific surface area up to 46 m²). The polymers readily under go quantitative transcacetalization. Soluble poly(2-formylethyl methacrylate) (8) was prepared by radical polymerization in solution. Copolymers of 2-formylethyl methacrylate (7) with 4 and 5 were prepared by suspension polymerization in the bead form (diameter 75 – 350 μm; specific surface area up to 128 m²/g). The aldehyde group of these polymers is sensitive to oxidation in air. The content of aldehyde groups was measured spectrometrically and by reaction with 1,2-ethanedithiol.     

Synthesis and thermodynamic studies of two new polymers carrying amido and amino groups in the side chains

Two linear vinyl polymers carrying amido and primary amino groups in the side chains were synthesized and characterized. Their behaviour in aqueous solution was investigated by potentiometric, viscometric and calorimetric techniques. In both cases, the basicity constants show a linear dependence on the degree of protonation α, while the enthalpy values of protonation do not. The thermodynamic results demonstrate the important role of hydrophobic interactions on the protonation process.     

Synthesis,characterization and polymerization of dendrimers with methacrylic end groups

Dendritic methacrylic crosslinking agents were synthesized by modification of amino functional poly(propyleneimine) dendrimers. On the basis of model reactions, several experimental methods for the introduction of methacrylate end groups were evaluated. In case of the Michael reaction of 2-(acryloyloxy)ethyl methacrylate (1) the amino-end groups of the dendrimers of the second, the fourth or the fifth generation add exclusively onto the acrylic double bonds of 1 forming methacrylic end groups in the modified dendrimers. The quantitative and uniform conversion could be proved by NMR spectroscopy. Analogous dendrimer modifications were carried out with mixtures of 1 and other acrylates. The dendrimeric methacrylates of different generations were polymerized in solution and bulk at 80°C with 2.2′-azoisobutyronitrile as initiator. The polymerization enthalpy of the dendrimeric methacrylates was determined by differential scanning calorimetry and shows that the polymerization of approximately every double bond takes place. The polymerization of methacrylic dendrimers yields crosslinked polymers with glass transition temperatures near or below room temperature.     

Aldehydes and acetals based on esters of methacrylic acid as potential monomers

New monomers containing aldehyde groups in the alcohol component of methacrylates were prepared. The structure of these monomers prevents undesired spontaneous intramolecular cyclization reactions of pendant aldehyde groups of the corresponding polymers. 2,2-Diethoxyethyl methacrylate (1) and its saturated analog, 2,2-diethoxyethyl pivalate (3) and 3,3-diethoxypropyl methacrylate (2) were prepared. The conditions for a selective hydrolysis of the acetal function of these compounds, leading to the corresponding aldehydes, were studied.     

Synthesis and characterization of liquid-crystalline copolymers with dichroic dyes and mesogens as side groups

Liquid-crystalline copolymers with covalently attached dichroic dyes were synthesized and characterized. Copolymers with high anthraquinone and trisazo-dye content were obtained by copolymerization of dye monomers with 4-cyanophenyl 4-(6-acryloyloxyhexyloxy)benzoate ( 1 ) and 6-acryloyloxyhexyl 4-(trans-4-propylcyclohexyl)benzoate ( 2 ). Particular attention is given to the influence of the dye content and the dye structure on the liquid-crystalline behavior of the copolymers.     

Synthesis and characterization of copolymers from acrylamide and methacrylamide carrying peptide side chains

N-Benzylacrylamide ( 1 ) and N-(3-aminopropyl)methacrylamide hydrochloride ( 2 ) were copolymerized to give poly[N-benzylacrylamide-co-N-(3-aminopropyl)methacrylamide hydrochloride] ( 3 ). The reactivity ratios r₁ and r₂ were found to be r₁ = 0,87 and r₂ = 0,66 in which r₁r₂ < 1 indicate a statistical copolymer composition. Dehydrochlorination of the copolymer liberated primary amino groups to which peptide chains were grafted by reaction with L -alanine-NCA. The solubility of the resulting graft copolymers ( 6 ) in trifluoroacetic acid allowed the characterization of the products both by NMR and polarimetry. These methods and IR spectroscopy showed that the primary amino groups have only partially participated in initiating the NCA polymerization. The length of grafted peptide chains was found to be always higher than the one calculated from the ratio [NCA]/[NH₂].     

Synthesis and characterization of some novel polyamides containing diacetylene side groups

A series of novel polyamides containing diacetylene groups as side chains were prepared by Cadiot-Chodkiewcz-coupling of polymer precursors bearing 2-propynyloxy side groups with 4-bromo-3-butyn-1-ol. The conversion of the acetylenic groups was in the range of 87.5–96.5% depending on the chemical structure of the polymer backbone. The polymers are highly amorphous and undergo random cross-linking on heating. Thermally treated polymer films show third-order nonlinear optical susceptibility χ(3) of the order of 10⁻¹⁰ esu (= 10⁻¹⁸m⁵/V²).     

Synthesis and cation-sensitive fluorescence of polyelectrolytes bearing crown ether side groups

Polyelectrolytes bearing crowned acetophenone moieties were prepared by radical copolymerization of 4′-acryloylbenzo-18-crown-6

1 System. name of benzo-18-crown-6: 1,2-benzo-1,4,7,10,13,16-hexaoxa-2-octadecene.

and methacrylic acid or lithium 2-acrylamido-2-methyl-1-propanesulfonate. On excitation with 330 nm light the polymers showed fluorescence at 410 nm in a mixed solvent of methanol and water (1:9 v/v) at 30°C. When cations were added, the fluorescence intensity of the polymers decreased in the orders Li⁺ > Na⁺ > Cs⁺ > Rb⁺ > K ⁺ for alkali metal cations, Ca²⁺ > Sr²⁺ > Ba²⁺ for alkaline earth metal cations and C₂H₅NH₂ > CH₃(CH₂)₃NH₂ > C₆H₅CH₂NH₂ for alkylamine hydrochlorides used. The concentration effect for cations in the neighborhood of the polymer-bound crown ether groups by electrostatic and/or hydrophobic binding induced significant complex formation between cations and crown ethers in aqueous solutions, resulting in a decrease of the fluorescence intensity.     

Effect of structure on glass transition temperatures of poly(methacrylic ester)s with bulky side groups

The values of the vitreous transition temperature, T_g, of three poly(methacrylic ester)s having bulky side groups are correlated with structural effects. T_g has been obtained experimentally by means of differential calorimetry and by the tensiometric method suggested by Ferroni. The experimental values of T_g agree well with the calculated ones obtained by the method of Van Krevelen. The values of T_g determined by differential calorimetry are markedly affected by the heating rate and by the molecular weight of the fractions. The solubility parameters of the polymers studied have been estimated. Poly(p-tert-butylphenyl methacrylate), (BPh), exhibits higher values for the solubility parameter, the steric hindrance parameter σ and the glass transition temperature T_g than poly(p-tert-butylcyclohexyl methacrylate), (BCy), and poly(neopentyl methacrylate), (NPe). These results have been interpreted in terms of intermolecular forces and steric hindrance effects, which would be greater in BPh than in BCy and NPe.     

Synthesis of polyorganosiloxanes with imidazolyl groups in the side chain

An imidazolyl ring was introduced into the side chain of poly(3-chlorocarbonylpropylmethyl-siloxane) ( 4 ) by esterification with 4(5)-hydroxymethylimidazole ( 1 ), the imino group being protected during esterification by the 2-nitrobenzyl group which can be easily cleaved by UV light irradiation without attacking the main chain. The photolytic cleavage of the 2-nitrobenzyl group was completed with a yield of ≈ 100% after 2 h without any remarkable side reaction. The polyorganosiloxanes ( 6 ), with a high content of imidazolyl groups in the side chain, are slightly soluble in hot DMSO and DMF. From this fact, in addition to the result of the measurement of T_g, it is suggested that very strong intermolecular hydrogen bonds are operating.