Lisbeth Ahjopalo

On the molecular recognition and associations between electrically conducting polyaniline and solvents

The specific interactions between sulphonic acid protonated polyaniline (PANI) and solvents are here studied both by the semiempirical AM1 method and experimentally. Phenolic solvents are shown to have a relatively large interaction with the sulphonate anions of the counterions and with the amines in PANI. In addition, a properly functionalized counterion may form cyclic associations provided that there is a steric match between the molecules concerned. This concept is called molecular recognition and it is a novel concept in the context of PANI. For example, the carbonyl group in (±)‐10‐camphor sulphonic acid (CSA) can form a hydrogen bond to the hydroxyl group of m‐cresol, whereby the phenyl ring becomes coplanar with one of the PANI rings thus enabling enhanced van der Waals interaction. This additional specific interaction agrees with our observed increased solubility with CSA doped PANI in m‐cresol, compared to its solubility in dimethyl sulphoxide or chloroform, or to tosylene sulphonic acid doped P...

Processible polyaniline complexes due to molecular recognition: Supramolecular structures based on hydrogen bonding and phenyl stacking

Abstract We show that sulphonic acid doped polyaniline (PANI) can be plasticized using certain low-acidic organic compounds consisting of ring structures and hydrogen bonding moieties that are able to “recognize” the complementary moieties of the doped PANI. The achieved synergistic combination of interactions consists of phenyl stacking, hydrogen bonding and charge transfer due to protonation. Fusible electrically conducting supramolecular structures are rendered, as suggested also by quantum chemical calculations. For example, PANI doped by methanesulphonic acid, toluenesulpnonic acid, dodecylbenzenesulphonic acid, or camphorsulphonic acid can be plasticized by dihydroxybenzenes and bisphenols to obtain fusible particle-free films at the resolution of optical microscope. The generalization to other plasticizers and other aromatic polymers, such as polypyrrole, is obvious.

Cyclic oligomers in saturated polyesters

Abstract To get an in-depth understanding of the structure–property relationship in saturated polyester resins, the reactivity of various diols and diacids as well as reaction conditions were studied. Adipic acid (AA), phthalic anhydride (PA), isophthalic acid (IPA), terephthalic acid (TPA), 2-butyl-2-ethyl-1,3-propanediol (BEPD) and 2,2-dimethyl-1,3-propanediol (NPG) were addressed. It was found that in addition to linear oligomers with carboxyl and/or hydroxyl end groups cyclic oligomers were detected. Cyclic dimers of TPA and NPG are known to migrate to the coating surface causing “blooming”. The understanding of this phenomenon and the monomers capable of forming cyclic dimers are the subject of this study, where we combined molecular modeling and analytical characterization. The probability of the formation of macrocyclic structures was shown to decrease in the order: BEPD–PA>BEPD–AA≥BEPD–IPA>BEPD–TPA. The temperature dependence was found to be small.

Copolymerization of ethylene and non-conjugated dienes with Cp2ZrCl2/MAO catalyst system: effect of polymerization temperature on the copolymer structure

Abstract Ethylene was copolymerized with linear, non-conjugated dienes by the metallocene catalyst system Cp2ZrCl2/MAO at several temperatures from 20 to 80°C. The dienes were 1,5-hexadiene (HD), 1,7-octadiene (OD) and 7-methyl-1,6-octadiene (MOD). Incorporation of the dienes was studied by 1 H and 13 C NMR and FTIR. Polymerization conditions had a dramatic effect on the degree of crosslinking of the product. At polymerization temperatures from 20 to 65°C the copolymers of ethylene and HD or OD were nearly totally crosslinked, whereas at 80°C the degree of crosslinking was consistently under 10%. When MOD was used as comonomer the degree of crosslinking did not increase above 40% even for copolymer produced at 20°C.

Molecular modeling of metallocene catalyzed copolymerization of ethylene with functional comonomers

Abstract Metallocene catalyzed copolymerization of ethylene with comonomers having polar functional groups (alcohols, carboxylic acids and esters) has been studied experimentally and by molecular modeling. The polar functional groups strongly reduce the activity of the catalyst. The deactivation of the catalyst is investigated with DFT calculations on some model systems. The effect of the spacer length between the double bond and the functional group is analyzed using molecular dynamics and molecular mechanics methods, and compared with experiments.