Luigi Angiolini | Università di Bologna (original) (raw)

Papers by Luigi Angiolini

Chemistry of Materials, 2009

Room-temperature photorefractivity without prepoling was demonstrated in polymers and copolymers ... more Room-temperature photorefractivity without prepoling was demonstrated in polymers and copolymers with a glass transition temperature well above 100°C. The compounds used are multifunctional sidechain polymers exhibiting chiral, semiconducting, photochromic, and nonlinear optical (azoaromatic moieties) properties. The photorefractive performance was linked to the reorientational effect of the photogenerated space-charge field, which well below the glass transition temperature can be active in the presence of the conformational mobility achieved via the trans-cis light-induced isomerization. The grating build-up time, which is long at λ ) 633 nm (with a time constant τ ≈ 500-1000 s) decreases by 2 orders of magnitude at λ ) 532 nm, where absorption is higher.

Macromolecular Chemistry and Physics, 2009

Sensors and Actuators B: Chemical, 2007

We present here a preliminary report on the interaction between a new class of chiral azo-polymer... more We present here a preliminary report on the interaction between a new class of chiral azo-polymers with protic acids. The experiments have been carried out on amorphous thin films obtained by spin coating. The investigated polymers display reversible changes of their UV–vis spectra and chiroptical properties (evidenced by circular dichroism measurements) in response to external chemical stimuli, thus suggesting their potential use as ultrathin thermoplastic sensors.

Reactive and Functional Polymers, 2012

... Optically active methacrylic copolymers with side-chain azoaromatic and 9-phenylcarbazole moi... more ... Optically active methacrylic copolymers with side-chain azoaromatic and 9-phenylcarbazole moieties Luigi Angiolini*1, Loris Giorgini1, Francesco Mauriello2 and Paul ... beam is nearly parallel to the writing beam and the films are sufficiently thin so that the Bragg condition about ...

Macromolecular Chemistry and Physics, 2008

ABSTRACT Two novel optically active polymethacrylates bearing in the side chain a cyclic chiral g... more ABSTRACT Two novel optically active polymethacrylates bearing in the side chain a cyclic chiral group of one prevailing absolute configuration linked to the carbazole chromophore, deriving from the related monomers (S)-(-)-3-methacryloyloxy-N-[3-(9-ethylcarbazolyl)]pyrrolidine [(S)-(-)MECP] and (S)-(+)-2-methacryloyl.oxy-N-[3-(9-etliylcarbazolyl)]succinimide [(S)-(+)-MECSI], have been prepared and characterized with the aim to obtain materials suitable to photoconductive applications. Poly[(S)-(-)-MECP] and poly[(S)-(+)-MECSI] exhibit remarkable thermal stability, with glass transition temperature around 200 degrees C and decomposition temneratures in the range 330-350 degrees C. Spectroscopic, thermal and chiroptical characterizations indicate the occurrence of dipolar interactions among the side chain moieties and the presence of chiral conformation at least for chain segments of the macromolecules. The photoconductive properties are discussed in terms of extent of conjugation in the side chain based on the electron-acceptor or electron-donator properties of the optically active ring linked to the carbazole group.

Room-temperature photorefractivity without prepoling was demonstrated in polymers and copolymers ... more Room-temperature photorefractivity without prepoling was demonstrated in polymers and copolymers with a glass transition temperature well above 100°C. The compounds used are multifunctional sidechain polymers exhibiting chiral, semiconducting, photochromic, and nonlinear optical (azoaromatic moieties) properties. The photorefractive performance was linked to the reorientational effect of the photogenerated space-charge field, which well below the glass transition temperature can be active in the presence of the conformational mobility achieved via the trans-cis light-induced isomerization. The grating build-up time, which is long at λ ) 633 nm (with a time constant τ ≈ 500-1000 s) decreases by 2 orders of magnitude at λ ) 532 nm, where absorption is higher.

Chemistry - A European Journal, 2008

The synthesis of chiral liquid-crystalline polymers of well-controlled structure (linear and thre... more The synthesis of chiral liquid-crystalline polymers of well-controlled structure (linear and three-armed star-shaped) with distinct average chain lengths and low polydispersity was achieved by atom transfer radical polymerisation (ATRP) of a new optically active monomer (S)-4-[6-(2-methacryloyloxypropanoyloxy)hexyloxy)]-4'-ethoxyazobenzene [(S)-ML6A], containing the L-lactic residue of one absolute configuration in the side-chain. All the obtained polymeric samples, characterised by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and polarised optical microscopy (POM), exhibit a smectic A(1/2) (fully interdigitated) liquid-crystalline phase and high cleaning points, with transition temperatures dependent on the average polymerisation degree and the macromolecular structure. The chirality originated at the molecular level by the asymmetric functionality of the L-lactic acid residue provides the polymers, in the smectic phase, of highly homogeneous conformations with a prevailing chirality related to the presence of H-aggregates having conformational dissymmetry of one prevailing screw-sense. By irradiating with circularly polarised light (CPL), it is possible to photomodulate the chiroptical properties of these intrinsically chiral polymeric thin films. Upon irradiation with left-handed CPL (l-CPL), the circular dichroism (CD) spectra of the films show enhancement of ellipticity and a net inversion of sign. The effect is reversible and the mirror image of the CD spectrum can be restored by pumping with right-handed CPL radiation (r-CPL). The results show the ability of l-CPL to invert the supramolecular chirality of the materials and demonstrate the essential role of azoaromatic aggregates.

Molecular Crystals and Liquid Crystals, 2009

ABSTRACT A brush polymer containing photosensitive mesogenic side chains has been directly synthe... more ABSTRACT A brush polymer containing photosensitive mesogenic side chains has been directly synthesized on glass substrates by a grafting method involving polymerization of a metacrylic azobenzenic monomer under Atomic Transfer Radical Polymerization (ATRP) conditions. Brush polymer surfaces, with respect to more traditional films, are resistant to solvents and to high temperatures due to the covalent bonds between chain and substrate, which stabilizes the film morphology. The peculiar characteristics of the present polymeric brushes, namely the intrinsic in-plane orientation of the mesogenic units located in the side chains, together with the possibility of a fine control on the structure, make them very attractive for application as command surfaces. We then employed such brushes as photo-controllable command surfaces in twisted/planar switchable cells filled with a low molecular weight liquid crystal and we characterized the molecular order at interface by means of confocal polarized Raman microscopy.

e-Polymers, 2008

Corona poling behaviours of optically active photochromic copolymers derived from methyl methacry... more Corona poling behaviours of optically active photochromic copolymers derived from methyl methacrylate (MMA) and the methacrylic ester of (S)-3hydroxy pyrrolidine linked through the nitrogen atom to the highly conjugated photochromic 4'-(β-cyano-β-(methylsulfonyl)vinyl)-4-azobenzene moiety, have been investigated with the aim to evaluate the effect on the non-linear optical (NLO) properties originated by the presence of inactive side-chain MMA groups along the main chain. The NLO properties of in situ corona poled polymeric films have been studied by second harmonic generation (SHG) measurements. The d 33 values of the investigated polymers were determined to be in the range 10-86 pm/V after corona poling. The temporal and thermal stability of the optimal SHG signals obtained after corona poling process of all the macromolecular materials has been investigated and compared. The results indicate that the maximum of these properties can be obtained at a molar content of photochromic units around 20-40%.

ABSTRACT A novel multicomponent polymer poly[(S)-ML-PPCA], bearing three distinct functional grou... more ABSTRACT A novel multicomponent polymer poly[(S)-ML-PPCA], bearing three distinct functional groups (i.e. azoaromatic, carbazole and chiral of one single configuration) jointly linked to the side chain has been synthesized and its properties compared to those of a similar derivative poly[M-PPCA], lacking of the chiral moiety, as far as photochromism and photoconductivity are concerned.Due to the presence of the chiral moiety, poly[(S)-ML-PPCA], besides higher optical activity than the related monomer, displays additional chiroptical properties with respect to poly[M-PPCA], allowing in particular the assessment of its photoresponsive properties connected to the trans-cis isomerization of the azoaromatic double bond by circular dichroism measurements and giving therefore the possibility of application as chiroptical switch too.

Optoelectronics - Materials and Techniques, 2011

Molecular Crystals and Liquid Crystals, 2009

ABSTRACT Novel optically active multifunctional methacrylic copolymers bearing in the side chain ... more ABSTRACT Novel optically active multifunctional methacrylic copolymers bearing in the side chain azoaromatic and carbazole groups linked to the main chain with a chiral rigid group of one prevailing absolute configuration have been prepared and characterized in order to observe possible effects on the optical activity of the resulting materials. All the polymeric derivates have good thermal stability with glass transition temperature around 200°C and high decomposition temperatures in the range 280-300°C. Spectroscopic, thermal and chiroptical characterizations indicate the occurrence of dipolar interactions between side chain moieties and the presence of an ordered chiral conformation at least for chain segments of the macromolecules.

Synthetic Metals, 2003

The photoinduced chiroptical properties of an optically active methacrylic polymer bearing in the... more The photoinduced chiroptical properties of an optically active methacrylic polymer bearing in the side-chain a conjugated trans-azoaromatic chromophore linked to the main chain through a chiral cyclic pyrrolidine moiety of one prevailing absolute configuration have been investigated. The polymeric film is characterized by a strong optical activity that can be amplified and reversibly modulated by irradiation with circularly polarized (CP) light at 488 nm. A remarkable modification of the shape of the circular dichroism (CD) spectrum after the initial irradiation steps is observed, with an amplification of the CD signal upon increasing the total irradiation fluence. The most important results are connected with the handedness of the CP radiation: left circularly polarized (CP-L) light is able to reverse the relative sign of the CD spectra, whereas by pumping with right circularly polarized (CP-R) radiation, it is possible to recover the original shape of the signal. This well reproducible and reversible effect suggests the possibility to use the investigated material for chiroptical switching.

Macromolecular Chemistry and Physics, 2007

... Luigi Angiolini,; Tiziana Benelli,; Loris Giorgini. Article first published online: 21 AUG 20... more ... Luigi Angiolini,; Tiziana Benelli,; Loris Giorgini. Article first published online: 21 AUG 2007. DOI: 10.1002/macp.200700160. ... Measurements. 1 H and 13 C NMR spectra were obtained at room temperature, on 5–10% CDCl 3 solutions, using a Varian NMR Gemini 300 spectrometer ...

Macromolecular Symposia, 2006

Novel optically active homopolymeric polymethacrylates have been synthesized by radical polymeriz... more Novel optically active homopolymeric polymethacrylates have been synthesized by radical polymerization of the corresponding monomers (S)-3-methacryloyloxy-1-(4-azobenzene)pyrrolidine and (S)-3-methacryloyloxy-1-(4 H -nitro-4-azobenzene)pyrrolidine. The polymers are characterized by the presence in the side chain of an optically active chiral moiety linked to the trans-azoaromatic system through the pyrrolidine nitrogen atom, which allows the establishment of a donor±acceptor conjugated system. The thermal properties of the polymeric derivatives indicate an appreciable thermal stability and increased glass transition temperature values with respect to similar polymeric derivatives bearing in the side chain the conjugated trans-azoaromatic chromophore. UV and circular dichroism spectra in solution suggest that dipolar interactions between the chromophores are present in the polymeric derivatives and that the macromolecules assume for chain sections dissymmetric conformations with a prevailing screw sense, induced by the presence of the conformationally rigid optically active cyclic moiety. This gives rise to much higher optical activity of the macromolecular systems with respect to that afforded by the structurally related low molecular weight compounds synthesized as models of the polymer repeating units, despite the low stereoregularity degree of the polymeric main chain. #

Journal of Polymer Science Part A: Polymer Chemistry, 1999

ABSTRACT Novel optically active polymethacrylates, namely poly[(S)-3-methacryloyloxy-1-(4-azobenz... more ABSTRACT Novel optically active polymethacrylates, namely poly[(S)-3-methacryloyloxy-1-(4-azobenzene)pyrrolidine] and poly[(S)-3-methacryloyloxy-1-(4′-nitro-4-azobenzene)pyrrolidine], have been synthesized by radical polymerization of the corresponding monomers, prepared in turn through a synthetic route preserving the asymmetric center by any racemization reaction. These homopolymers are characterized by the presence in the side chain of an optically active pyrrolidinyl ring linked to the trans-azoaromatic system through the nitrogen atom. The optical activity of the polymers in solution appears much higher than that observed with the low molecular weight models, purposely synthesized for comparison. Circular dichroism spectra of the synthesized products demonstrated that, in solution, the macromolecules assume highly homogeneous conformations with a prevailing chirality to a larger extent with respect to analogous systems previously investigated. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3257–3268, 1999

Macromolecules, 2006

... Luigi Angiolini,* † Tiziana Benelli, † Loris Giorgini ... The NMR spectra of monomers and low... more ... Luigi Angiolini,* † Tiziana Benelli, † Loris Giorgini ... The NMR spectra of monomers and low molecular weight intermediates were recorded with a Varian Gemini 300 spectrometer at room temperature on 5−10% solutions in CDCl 3 . Polymeric derivatives were run at 80 °C in p ...

Chemistry of Materials, 2009

Room-temperature photorefractivity without prepoling was demonstrated in polymers and copolymers ... more Room-temperature photorefractivity without prepoling was demonstrated in polymers and copolymers with a glass transition temperature well above 100°C. The compounds used are multifunctional sidechain polymers exhibiting chiral, semiconducting, photochromic, and nonlinear optical (azoaromatic moieties) properties. The photorefractive performance was linked to the reorientational effect of the photogenerated space-charge field, which well below the glass transition temperature can be active in the presence of the conformational mobility achieved via the trans-cis light-induced isomerization. The grating build-up time, which is long at λ ) 633 nm (with a time constant τ ≈ 500-1000 s) decreases by 2 orders of magnitude at λ ) 532 nm, where absorption is higher.

Macromolecular Chemistry and Physics, 2009

Sensors and Actuators B: Chemical, 2007

We present here a preliminary report on the interaction between a new class of chiral azo-polymer... more We present here a preliminary report on the interaction between a new class of chiral azo-polymers with protic acids. The experiments have been carried out on amorphous thin films obtained by spin coating. The investigated polymers display reversible changes of their UV–vis spectra and chiroptical properties (evidenced by circular dichroism measurements) in response to external chemical stimuli, thus suggesting their potential use as ultrathin thermoplastic sensors.

Reactive and Functional Polymers, 2012

... Optically active methacrylic copolymers with side-chain azoaromatic and 9-phenylcarbazole moi... more ... Optically active methacrylic copolymers with side-chain azoaromatic and 9-phenylcarbazole moieties Luigi Angiolini*1, Loris Giorgini1, Francesco Mauriello2 and Paul ... beam is nearly parallel to the writing beam and the films are sufficiently thin so that the Bragg condition about ...

Macromolecular Chemistry and Physics, 2008

ABSTRACT Two novel optically active polymethacrylates bearing in the side chain a cyclic chiral g... more ABSTRACT Two novel optically active polymethacrylates bearing in the side chain a cyclic chiral group of one prevailing absolute configuration linked to the carbazole chromophore, deriving from the related monomers (S)-(-)-3-methacryloyloxy-N-[3-(9-ethylcarbazolyl)]pyrrolidine [(S)-(-)MECP] and (S)-(+)-2-methacryloyl.oxy-N-[3-(9-etliylcarbazolyl)]succinimide [(S)-(+)-MECSI], have been prepared and characterized with the aim to obtain materials suitable to photoconductive applications. Poly[(S)-(-)-MECP] and poly[(S)-(+)-MECSI] exhibit remarkable thermal stability, with glass transition temperature around 200 degrees C and decomposition temneratures in the range 330-350 degrees C. Spectroscopic, thermal and chiroptical characterizations indicate the occurrence of dipolar interactions among the side chain moieties and the presence of chiral conformation at least for chain segments of the macromolecules. The photoconductive properties are discussed in terms of extent of conjugation in the side chain based on the electron-acceptor or electron-donator properties of the optically active ring linked to the carbazole group.

Room-temperature photorefractivity without prepoling was demonstrated in polymers and copolymers ... more Room-temperature photorefractivity without prepoling was demonstrated in polymers and copolymers with a glass transition temperature well above 100°C. The compounds used are multifunctional sidechain polymers exhibiting chiral, semiconducting, photochromic, and nonlinear optical (azoaromatic moieties) properties. The photorefractive performance was linked to the reorientational effect of the photogenerated space-charge field, which well below the glass transition temperature can be active in the presence of the conformational mobility achieved via the trans-cis light-induced isomerization. The grating build-up time, which is long at λ ) 633 nm (with a time constant τ ≈ 500-1000 s) decreases by 2 orders of magnitude at λ ) 532 nm, where absorption is higher.

Chemistry - A European Journal, 2008

The synthesis of chiral liquid-crystalline polymers of well-controlled structure (linear and thre... more The synthesis of chiral liquid-crystalline polymers of well-controlled structure (linear and three-armed star-shaped) with distinct average chain lengths and low polydispersity was achieved by atom transfer radical polymerisation (ATRP) of a new optically active monomer (S)-4-[6-(2-methacryloyloxypropanoyloxy)hexyloxy)]-4'-ethoxyazobenzene [(S)-ML6A], containing the L-lactic residue of one absolute configuration in the side-chain. All the obtained polymeric samples, characterised by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and polarised optical microscopy (POM), exhibit a smectic A(1/2) (fully interdigitated) liquid-crystalline phase and high cleaning points, with transition temperatures dependent on the average polymerisation degree and the macromolecular structure. The chirality originated at the molecular level by the asymmetric functionality of the L-lactic acid residue provides the polymers, in the smectic phase, of highly homogeneous conformations with a prevailing chirality related to the presence of H-aggregates having conformational dissymmetry of one prevailing screw-sense. By irradiating with circularly polarised light (CPL), it is possible to photomodulate the chiroptical properties of these intrinsically chiral polymeric thin films. Upon irradiation with left-handed CPL (l-CPL), the circular dichroism (CD) spectra of the films show enhancement of ellipticity and a net inversion of sign. The effect is reversible and the mirror image of the CD spectrum can be restored by pumping with right-handed CPL radiation (r-CPL). The results show the ability of l-CPL to invert the supramolecular chirality of the materials and demonstrate the essential role of azoaromatic aggregates.

Molecular Crystals and Liquid Crystals, 2009

ABSTRACT A brush polymer containing photosensitive mesogenic side chains has been directly synthe... more ABSTRACT A brush polymer containing photosensitive mesogenic side chains has been directly synthesized on glass substrates by a grafting method involving polymerization of a metacrylic azobenzenic monomer under Atomic Transfer Radical Polymerization (ATRP) conditions. Brush polymer surfaces, with respect to more traditional films, are resistant to solvents and to high temperatures due to the covalent bonds between chain and substrate, which stabilizes the film morphology. The peculiar characteristics of the present polymeric brushes, namely the intrinsic in-plane orientation of the mesogenic units located in the side chains, together with the possibility of a fine control on the structure, make them very attractive for application as command surfaces. We then employed such brushes as photo-controllable command surfaces in twisted/planar switchable cells filled with a low molecular weight liquid crystal and we characterized the molecular order at interface by means of confocal polarized Raman microscopy.

e-Polymers, 2008

Corona poling behaviours of optically active photochromic copolymers derived from methyl methacry... more Corona poling behaviours of optically active photochromic copolymers derived from methyl methacrylate (MMA) and the methacrylic ester of (S)-3hydroxy pyrrolidine linked through the nitrogen atom to the highly conjugated photochromic 4'-(β-cyano-β-(methylsulfonyl)vinyl)-4-azobenzene moiety, have been investigated with the aim to evaluate the effect on the non-linear optical (NLO) properties originated by the presence of inactive side-chain MMA groups along the main chain. The NLO properties of in situ corona poled polymeric films have been studied by second harmonic generation (SHG) measurements. The d 33 values of the investigated polymers were determined to be in the range 10-86 pm/V after corona poling. The temporal and thermal stability of the optimal SHG signals obtained after corona poling process of all the macromolecular materials has been investigated and compared. The results indicate that the maximum of these properties can be obtained at a molar content of photochromic units around 20-40%.

ABSTRACT A novel multicomponent polymer poly[(S)-ML-PPCA], bearing three distinct functional grou... more ABSTRACT A novel multicomponent polymer poly[(S)-ML-PPCA], bearing three distinct functional groups (i.e. azoaromatic, carbazole and chiral of one single configuration) jointly linked to the side chain has been synthesized and its properties compared to those of a similar derivative poly[M-PPCA], lacking of the chiral moiety, as far as photochromism and photoconductivity are concerned.Due to the presence of the chiral moiety, poly[(S)-ML-PPCA], besides higher optical activity than the related monomer, displays additional chiroptical properties with respect to poly[M-PPCA], allowing in particular the assessment of its photoresponsive properties connected to the trans-cis isomerization of the azoaromatic double bond by circular dichroism measurements and giving therefore the possibility of application as chiroptical switch too.

Optoelectronics - Materials and Techniques, 2011

Molecular Crystals and Liquid Crystals, 2009

ABSTRACT Novel optically active multifunctional methacrylic copolymers bearing in the side chain ... more ABSTRACT Novel optically active multifunctional methacrylic copolymers bearing in the side chain azoaromatic and carbazole groups linked to the main chain with a chiral rigid group of one prevailing absolute configuration have been prepared and characterized in order to observe possible effects on the optical activity of the resulting materials. All the polymeric derivates have good thermal stability with glass transition temperature around 200°C and high decomposition temperatures in the range 280-300°C. Spectroscopic, thermal and chiroptical characterizations indicate the occurrence of dipolar interactions between side chain moieties and the presence of an ordered chiral conformation at least for chain segments of the macromolecules.

Synthetic Metals, 2003

The photoinduced chiroptical properties of an optically active methacrylic polymer bearing in the... more The photoinduced chiroptical properties of an optically active methacrylic polymer bearing in the side-chain a conjugated trans-azoaromatic chromophore linked to the main chain through a chiral cyclic pyrrolidine moiety of one prevailing absolute configuration have been investigated. The polymeric film is characterized by a strong optical activity that can be amplified and reversibly modulated by irradiation with circularly polarized (CP) light at 488 nm. A remarkable modification of the shape of the circular dichroism (CD) spectrum after the initial irradiation steps is observed, with an amplification of the CD signal upon increasing the total irradiation fluence. The most important results are connected with the handedness of the CP radiation: left circularly polarized (CP-L) light is able to reverse the relative sign of the CD spectra, whereas by pumping with right circularly polarized (CP-R) radiation, it is possible to recover the original shape of the signal. This well reproducible and reversible effect suggests the possibility to use the investigated material for chiroptical switching.

Macromolecular Chemistry and Physics, 2007

... Luigi Angiolini,; Tiziana Benelli,; Loris Giorgini. Article first published online: 21 AUG 20... more ... Luigi Angiolini,; Tiziana Benelli,; Loris Giorgini. Article first published online: 21 AUG 2007. DOI: 10.1002/macp.200700160. ... Measurements. 1 H and 13 C NMR spectra were obtained at room temperature, on 5–10% CDCl 3 solutions, using a Varian NMR Gemini 300 spectrometer ...

Macromolecular Symposia, 2006

Novel optically active homopolymeric polymethacrylates have been synthesized by radical polymeriz... more Novel optically active homopolymeric polymethacrylates have been synthesized by radical polymerization of the corresponding monomers (S)-3-methacryloyloxy-1-(4-azobenzene)pyrrolidine and (S)-3-methacryloyloxy-1-(4 H -nitro-4-azobenzene)pyrrolidine. The polymers are characterized by the presence in the side chain of an optically active chiral moiety linked to the trans-azoaromatic system through the pyrrolidine nitrogen atom, which allows the establishment of a donor±acceptor conjugated system. The thermal properties of the polymeric derivatives indicate an appreciable thermal stability and increased glass transition temperature values with respect to similar polymeric derivatives bearing in the side chain the conjugated trans-azoaromatic chromophore. UV and circular dichroism spectra in solution suggest that dipolar interactions between the chromophores are present in the polymeric derivatives and that the macromolecules assume for chain sections dissymmetric conformations with a prevailing screw sense, induced by the presence of the conformationally rigid optically active cyclic moiety. This gives rise to much higher optical activity of the macromolecular systems with respect to that afforded by the structurally related low molecular weight compounds synthesized as models of the polymer repeating units, despite the low stereoregularity degree of the polymeric main chain. #

Journal of Polymer Science Part A: Polymer Chemistry, 1999

ABSTRACT Novel optically active polymethacrylates, namely poly[(S)-3-methacryloyloxy-1-(4-azobenz... more ABSTRACT Novel optically active polymethacrylates, namely poly[(S)-3-methacryloyloxy-1-(4-azobenzene)pyrrolidine] and poly[(S)-3-methacryloyloxy-1-(4′-nitro-4-azobenzene)pyrrolidine], have been synthesized by radical polymerization of the corresponding monomers, prepared in turn through a synthetic route preserving the asymmetric center by any racemization reaction. These homopolymers are characterized by the presence in the side chain of an optically active pyrrolidinyl ring linked to the trans-azoaromatic system through the nitrogen atom. The optical activity of the polymers in solution appears much higher than that observed with the low molecular weight models, purposely synthesized for comparison. Circular dichroism spectra of the synthesized products demonstrated that, in solution, the macromolecules assume highly homogeneous conformations with a prevailing chirality to a larger extent with respect to analogous systems previously investigated. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3257–3268, 1999

Macromolecules, 2006

... Luigi Angiolini,* † Tiziana Benelli, † Loris Giorgini ... The NMR spectra of monomers and low... more ... Luigi Angiolini,* † Tiziana Benelli, † Loris Giorgini ... The NMR spectra of monomers and low molecular weight intermediates were recorded with a Varian Gemini 300 spectrometer at room temperature on 5−10% solutions in CDCl 3 . Polymeric derivatives were run at 80 °C in p ...