Emanuele Paternò (Palermo, 1847-1935) si laureò a Palermo nel 1871, nello stesso anno divenne professore a Torino, l'anno successivo venne chiamato a Palermo, e successe poi a Cannizzaro nella Cattedra di Chimica Generale di Roma. Celebri sono le sue ricerche pionieristiche (1869) sul carbonio tetraedrico. Paternò passò poi ad occuparsi di crioscopia (1885), applicando tale metodo alla determinazione delle masse molecolari. Gli studi successivi (1889-1910) sullo stato colloidale furono di grande avanguardia in campo europeo, rivelando alcune proprietà di base dei colloidi. Egli poté dimostrare che si tratta di soluzioni in cui le molecole formano degli aggregati molecolari (micelle). La conclusione pioneristica che Paternò trasse da queste osservazioni fu che "la proprietà colloidale di una sostanza non è una proprietà intrinseca inerente alla molecola dei corpi, ma è una proprietà relativa che si manifesta in presenza di un solvente e di un altro no".

REFERENCES 1. Fields R, Rodriguez F, Finn R K, J. Appl. Polym. Sc i. 1974; 18, 3571. 2. Jun H S, Kim B O, Kim YC, Chang HN, Woo SI, J. Environ. Polym. Deg. 1994; 2, 9. 3. Witt U, Müller RJ, Augusta J, Widdecke H, Deckwer WD, Macromol. Chem. Phys. 1994; 195, 793. 4. Witt U, Müller RJ, Deckwer WD, J. Macromol. Pure Appl. Chem. 1995; A32, 851. 5. Witt U, Müller RJ, Deckwer WD, J. Environm. Polym. Deg. 1997, 5, 81. 6. Witt U, Müller RJ, Deckwer WD, Macromol. Chem. Phys., 1996; 197, 1525. 7. Koyama N, Doi Y, Macromolecules, 1996; 29, 5843. 8. Mochizuchi M, Mukai K, Yamada K, Ichise N, Murase S, Iwaya Y, Macromolecules 1997; 30, 7403. 9. Lee SH, Lee KH, Hong S K, J. Appl. Polym. Sci. 1997 ; 64, 1999. 10. C. G. Vonk, J. Appl. Cryst. (1973), 6, 148; 11. Carothers WH, Hill JW, J. Am. Chem. Soc. 1932; 54 , 1579. 12. Takiyama E, Niikura I, Hatano Y, US Patent No. 5 306 787, 1994. 13. Takiyama E, Fujimaki T, Seki S, Hokari T, Hatano, US Patent No. 5 310 782, 1994. 14. Iwaya Y, Mukai K, Kawanishi M, Nishinohara M, US Patent No. 5 504 148, 1996. 15. Aiioka M, Enomoto K, Suzuki K, Yamaguchi A, Bull. Chem. Soc. Jpn. A, 1995, 68, 2125. 16. Scandola M., Focarete M. L., Frisoni G., Macromolecul es, 1998, 31, 3846. Figure 1 STRUCTURE and PROPERTIES of the POLYESTERS ANALYSED Table 1 n° Sample Synthesis method Composition H-NMR ηsp/c (dl/g) Mn Mw Mw/Mn d Tm e (°C) Crystallinity f (%)

Matrix-assisted laser desorption/ionization mass spectrometry (MALDI) was used to determine the structure of the molecules produced in the thermo-oxidative degradation of Nylon 6 and Nylon 66, at 180°C and 250°C in air. The MALDI spectra of the thermo-oxidized nylons provide information on the structure and end groups of the oligomers produced in the oxidation process. Our results show that the thermo-oxidation of both Ny6 and Ny66 proceeds through a hydrogen abstraction and subsequent formation of hydroperoxide intermediates. The latter decompose, yielding oligomers containing aldehydes, amides and methyl terminal groups. The aldehydes undergo further oxidation to produce carboxylic end groups. The formation of cyclopentanone terminal groups is also observed in the case of Nylon 66. Oligomers with structures deriving from Norrish-type degradation processes were not detected here for either Ny6 or Ny66.

We report matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and off-line coupling of size-exclusion chromatography with MALDI-TOFMS analysis (SEC/MALDI-TOFMS) methods for the detailed characterization of poly[(R,S)-3-hydroxybutyrate-co-L-lactic acid], P[(R,S)-3HB-co-LA], and poly[(R,S)-3-hydroxybutyrate-co-epsilon-caprolactone], P[(R,S)-3HB-co-CL], copolymer samples which are expected to be used in special medical application as scaffolds for cartilage and soft tissue engineering. The novel copolyesters contained randomly distributed (R,S)-3-hydroxybutyrate structural units, were synthesized by transesterification of the corresponding homopolymers, i.e. atactic poly[(R,S)-3-hydroxybutyrate], a-PHB, and poly(L-Lactide) (PLLA) or poly(epsilon-caprolactone) (PCL), respectively. The MS methods used for the characterization of the resulting polydisperse copolyester samples were supported by classical methods (NMR, SEC). The structures of individual copolyester macromolecules, including end-group chemical structures, were established using initially MALDI-TOFMS and then SEC/MALDI-TOFMS. The compositions of the copolyesters were determined by two methods, namely based on 1H NMR and MALDI-TOF spectra. The two sets of values showed good agreement. The sequence distribution was determined using the signal intensities of individual copolyester macromolecules, which appeared in MALDI-TOF mass spectra. Furthermore, sequence analysis gave information about the degree of transesterification. The copolyesters synthesized, with only one exception, were demonstrated to be almost random, which implies that the ester-ester exchange was close to completion.

In recent years, matrix assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectroscopy has become a routine analytical tool for the structural analysis of polymers, complementing NMR and other traditional techniques, a noteworthy change with respect to the past, when mass spectrometry (MS) was seldom used. In this review, we discuss salient aspects of MALDI. First, we devote a section to fundamentals and practice in MALDI of polymers (such as the laser, ion source, ion optics, reflectron, detector, ionization efficiency) as well as to some basic concepts of sample preparation (such as the MALDI matrix and cationization agents). Then, we focus on measurable quantities of polymers: average molar masses, the chemical formula and the structure of the monomer (actually of the repeat unit), the masses of the chain end groups, etc. In-depth coverage is given of coupling MALDI with liquid chromatography (LC), since often LC offers valuable help in exploring macromolecules. The final section is devoted to recent applications, with a detailed discussion of MALDI of addition polymers, condensation polymers, polymers with heteroatoms in the chain, copolymers and partially degraded polymers.

Thermal oxidation and photooxidation processes occurring in poly 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl] propane dianhydride-1,3-phenylendiamine copolymer (ULTEM), were investigated and compared. The study aimed at finding possible differences in the oxidation pathways of this complex polymer by using the analytical power of MALDI techniques. ULTEM films were subjected to photooxidation by exposure at 60 degrees C in a LW accelerated chamber (Q-UV Panel) in atmospheric air, and the oxidative process was followed as a function of the exposure time. Relevant structural information on the photooxidized ULTEM species was extracted from the MALDI spectra. These data show the presence of polymer chains containing acetophenone, phenyl acetic acid, phenols, benzoic acid, plithalic anhydride, and plithalic acid end groups. The mechanisms accounting for the formation of photooxidation products of Ultem involve several reactions: (i) photocleavage of methyl groups of the N-methyl phthalimide terminal units; (ii) photooxidative degradation of the isopropylidene bridge of BPA units; (iii) photooxidation of plithalimide units to phthalic anhydride and plithalic acid end groups. Some of these cleavage pathways are specific for the photooxidation process and the oligomers deriving from them are absent in the thermal by oxidized Ultem samples, whereas the thermal cleavage of the diphenyl ether units appears to occur only in the thermal oxidation process.

Poly(ester amide)s from dimethyl sebacate or sebacic acid and 2-aminoethanol or 4-amino-1-butanol were characterized by post-source decay matrix-assisted laser desorption/ionization time-of-flight (PSD-MALDI-TOF) and time-of-flight/time-of-flight tandem mass spectrometry (MALDI-TOF/TOF-MS/MS). Sodiated oligomers were selected as precursor ions for dissociation studies. PSD analysis was performed on dimethyl sebacate, dicarboxylic, carboxylic and amino alcohol, and diamino alcohol terminated oligomers. PSD-MALDI-TOF mass spectra yielded information on the fragmentation mechanisms of the poly(ester amide) chains, showing that the main cleavages proceed through a beta-hydrogen transfer rearrangement. MALDI-TOF/TOF-MS/MS provided structural information concerning ester/amide sequences in the polymer chains. As expected, together with the ions appearing in the PSD-MALDI mass spectrum, several new abundant fragment ions in the low-mass range are present in MALDI-TOF/TOF-MS/MS spectra. These new product ions proved to be diagnostic and made it possible to establish the presence of random sequences of ester and amide bonds in the poly(ester amide)s samples.

Poly{2,2-bis [4-(3,4-dicarboxyphenoxy)phenyl] propane dianhydride-1,3-phenylendiamine} copolymer (ULTEM) was subjected to thermoaging in an attempt to determine the structure of the species formed during oxidative degradation. The oxidative process was followed as a function of exposure time by using MALDI-TOF MS. Thermal oxidation produces charring after only 15 min and the formation of insoluble residue amounts to 50% after 180 min at 350 degrees C. Highly valuable structural information (including the end groups) was extracted from the MALDI spectra of the thermally oxidized ULTEM soluble samples. Oxidized specimens contained acetophenone, phenylacetic acid, phenols, benzoic acid, bisphenol A, phthalimide, and phthalic anhydride end groups. The mechanisms accounting for their formation involve several reactions: (i) cleavage of the diphenyl ether units; (ii) oxidative degradation of the isopropylidene bridge of BPA units; (iii) thermal cleavage of phenylphthalimide units.

In the last few years, mass spectrometry has rapidly become indispensable in polymer analysis and complements, in many ways, the structural data provided by nuclear magnetic resonance. Mass spectrometry of polymers is emerging as a revolutionary technique, capable of challenging the techniques and protocols established for years for the characterization of synthetic polymers. Matrix-assisted laser desorption/ionization (MALDI) has become a widely applied method for the structural characterization of synthetic polymers. The primary aim of this review is to illustrate some recent advances in the study of macromolecular systems by MALDI. MALDI allows the identification of repeat units and end groups, the structural analysis of linear and cyclic oligomers and the estimate of composition and sequence for co-polymers. MALDI is also quite useful for the measurement of molar mass and bivariate distributions in polymers and for the detection of self-association in macromolecules, performed by coupling MALDI with size exclusion chromatography (SEC). Recently MALDI has been applied, with remarkable success, to the study of thermal and oxidative processes in polymers and to the characterization of co-polymers obtained by reactive polymer blending. Selected applications of MALDI to polymers are illustrated herewith.

Matrix-assisted laser desorption ionization mass spectrometry (MALDI) was used to determine the structure of the molecules produced in the photooxidative degradation of nylon-66 at 60 degreesC in air. The MALDI spectra of the photooxidized nylon-66 (Ny66) show the presence of nearly 40 compounds, as compared to only four in the original Ny66 sample, and provide information on the structure and end groups of the oligomers produced in the oxidation. The structural analysis of the photooxidized species provided by the MALDI spectra allowed drawing a detailed map of the photodecomposition mechanisms of Ny66. Our results extend the currently accepted picture for the photooxidation mechanisms of Ny66, confirming previous insights into the hydrogen abstraction and subsequent formation of a hydroperoxide intermediate, but also reveal that Norrish I and Norrish II chain cleavage reactions play an important role in the photooxidation process of Ny66. Ny66 films exposed for 12 h show the appearance of only photooxidation products generated by the hydrogen peroxide decomposition, indicating that the chain photocleavage reactions Norrish I and Norrish II type do occur at a later stage of irradiation. An explanation is offered for the appearance of this induction period. It is expected that future MALDI studies may have an impact on the current views on photooxidation processes of other polymer systems.

A series of aliphatic copolyesters was obtained from (R,S)-beta-butyrolactone and two isomeric hydroxy acids, 6-hydroxyhexanoic and (R,S)-2-hydroxyhexanoic acids. The reactions were conducted in bulk without catalyst. Electrospray ionization tandem mass spectrometry (ESI-MSn) was used for molecular characterization of these copolyester oligomers. The mass spectra of the copolyesters studied have enabled identification of their molecular structures including chemical nature of the end groups (hydroxyl and carboxylate). The compositions of the oligocopolyesters and their sequence distributions were determined based on measurement of the relative intensities of the individual oligocopolyester peaks in the ESI mass spectra. The mass spectra (MS1) provided information on composition and sequence distribution, and small deviations from Bernoulli statistics were detected. The arrangement of co-monomer structural units along the oligopolyester chains was verified by MS/MS experiments and investigation of the fragmentation pathways.

A series of high molar mass aliphatic homo- and co-polyesters was obtained from 1,4-butandiol and methyl esters of succinic, adipic, sebacic acids, and these materials were characterised by 1H NMR, SEC, DSC, X-ray and viscosity. Good filmability was achieved for all the polymers. The biodegradability of poly(butylene succinate-co-butylene sebacate), P(BSu-co-BSe), and poly(butylene succinate-co-butylene adipate), P(BSu-co-BAd), samples, with different composition, was investigated under controlled soil burial conditions. Film samples were also assayed to enzymatic attack by lipase from Mucor miehei or from Rhizopus arrhizus. The biodegradation was evaluated as weight loss and the relative normalised weight loss rates were compared. The influence of crystallinity, molar mass, chemical structure and melting temperature upon biodegradation was studied. The weight loss of poly(3-hydroxy butyrate), P(HB), of poly(3-hydroxy butyrate-co-3-hydroxy valerate) 76/24, P(HB-co-HV) 76/24, and of two commercial Bionolle samples, was also investigated under soil burial conditions. The results allow a direct comparison of the soil burial degradability of polyesters having different structures.

Ny6-Ny6,10 and Ny6-Ny4,6 copolyamides prepared by a facile melt mixing at 290-310 degreesC of carboxyl terminated Nylon6 (Ny6-COOH) with Ny6,10 or Ny4,6, were characterized by MALDI, C-13 NMR, and DSC analysis. The results, from one side show how facile is the high yield synthesis of random copolyamides via the melt mixing of the corresponding polyamides. What makes the synthesis so facile is the use of a carboxyl terminated polyamide (Ny6-COOH) to attack the other polyamide (Ny4,6 or Ny6,10), as described herewith. The DSC data acquired provide a clear picture of the process. The second relevant point is about the sequence analysis of the copolyamides, made using their C-13 NMR spectra. The sequence has been derived directly from chain statistics principles, avoiding the use of inadequate procedures. To our knowledge, this is the first time as far as condensation copolymers are concerned. Interesting, the sequence analysis of our copolyamides has been also performed independently, by extracting pertinent information from their MALDI spectra. The results have been found in excellent agreement with those from C-13 NMR data.

Matrix-assisted laser desorption ionization mass spectrometry (MALDI-TOF-MS) has been found to be an excellent method to determine the structure of the molecules produced in the photooxidative degradation of poly(butylene succinate) (PBSu) at 60 degreesC in air. Over 20 compounds are present in the MALDI spectrum of the oxidized sample, as compared to only 4 in the original PBSu sample. The MALDI spectra present many new well-resolved peaks, which provide information on the structure and end groups of the oxidation products. The MALDI peaks correspond to sodiated ions of oxidized oligomers, and they have been assigned to polymer chains containing succinic and malonic acid, butyl ester, ethyl ester, and butyl formate end groups. These oligomers had not been revealed before. The mechanisms accounting for the formation of photooxidation products of PBSu involve the operation of several reactions: (i) oxidation of hydroxyl end groups; (ii) alpha-H abstraction decomposition; (iii) Norrish I photocleavage. Our results establish the photooxidation mechanisms of PBSu. The novelty of our approach consists of using a nonaveraging technique, such as mass spectrometry, which allows the detection of individual compounds formed during the oxidation process. This is a remarkable result, and it should be expected that future MALDI studies might have an impact on the current views on photooxidation processes of other polymer systems.

Matrix-Assisted Laser Desorption/Ionization (MALDI) allows the identification of repeat units and end groups, the structural analysis of linear and cyclic oligomers, and the estimate of composition and sequence for copolymers. MALDI has also been applied to the measurement of molar mass distributions in polymers and to the study of thermal and oxidative processes in polymers. This paper illustrates the detection of self-association in macromolecules made by coupling MALDI and Size Exclusion Chromatography (SEC), the investigation of polymer oxidation phenomena, and the characterization of copolymers formed in the processing of reactive polymer blends.

Several isothermal degradation experiments on poly(ethylene terephthalate) (PET) were conducted in the temperature range of 270-370 degreesC, in order to simulate the reactions that take place during the processing of PET under inert atmosphere (N-2) The structural characterisation of the reaction products was performed by MALDI mass spectrometry and by NMR analysis. The results indicate the formation of cyclic oligomers that decompose at higher temperature. Vinyl ester terminated oligomers could not be detected by MALDI and also by H-1 and C-13 NMR, whereas the formation of anhydride containing oligomers is well apparent. Formation of acetaldehyde in PET samples processed at various temperatures was detected by H-1 NMR. We have also included in the present study a set of experiments where 0.5%w P-(TsOHH2O)-H-. was added to PET. Our results show that the addition of small amounts of p-(TsOHH2O)-H-. to PET, heated at 270 and 285 degreesC, induces a strong hydrolytic reaction with consequent increase of carboxyl terminated polyester chains. (C) 2003 Elsevier Ltd. All rights reserved.

High molar mass random poly(butylene succinate-co-butylene sebacate), P(BS-co-BSe), and poly(butylene succinate-co-butylene adipate), P(BS-co-BA), with different composition, were synthesized and subjected to enzymatic hydrolysis by Lipase from Mucor miehei or from Rhizopus arrhizus. The enzymatic hydrolysis of P(BS-co-BSe)s and P(BS-co-BA)s films produced a mixture of water-soluble monomers and co-oligomers that were separated and identified by on-line high performance liquid chromatography/electrospray ionization mass spectrometry (HPLC/ESI-MS). Optimization of the HPLC analysis allowed the separation of isobar co-oligomers, differing only for the co-monomers sequence. Oligomers with the same monomer composition and molar mass but different sequence were identified by HPLC/ESI-MS-MS on-line analysis. The results obtained show a preferential hydrolytic cleavage induced by the lipases used. In particular, these enzymes prefer cleaving sebacic ester bonds in P(BS-co-BSe) copolymers, whereas succinic ester bonds appear to be hydrolyzed faster than adipic ester bonds in P(BS-co-BA) copolyesters. 1H NMR analysis further substantiates these findings. The primary products generated by lipase hydrolysis of polyester films underwent further degradation at longer reaction times. The HPLC/ESI-MS analysis of these mixtures at various times provided the first evidence that lipase catalysis is active also in water solution, a hydrophobic effect induced by the aliphatic units of these polyesters.

Poly 2,2-bis4-(3,4-dicarboxyphenoxy) phenylpropane dianhydride-1,3-phenylendiamine copolymer (ULTEM) was subjected to photo aging in the attempt to find evidence on the structure of the species formed in the oxidative degradation. The oxidation was followed as a function of the exposure time by MALDI and SEC/MALDI techniques. The SEC curves showed extensive degradation, with the formation of low molar mass oligomers having different end groups. Valuable structural information on the photo-oxidized ULTEM species was extracted from the MALDI spectra of the photo-oxidized ULTEM. These showed the presence of polymer chains containing acetophenone, phenyl acetic acid, phenols, benzoic acid, phthalic anhydride and phthalic acid end groups. The mechanisms accounting for the formation of photo-oxidation products involve several simultaneous reactions: (1) photo-cleavage of methyl groups of the N-methyl phthalimide terminal units; (2) photoxidative degradation of the isopropylidene bridge of BPA units; (3) photo-oxidation of phthalimide units to phthalic anhydride end groups: (4) hydrolysis of phthalic anhydride end groups. The kinetic behaviour of all the species detected is in agreement with the predictions of the reaction mechanisms hypothesized.

A combination of NMR and MALDI was found to be a suitable tool to study the exchange reactions that occur during the melt mixing of Nylon-6 and poly(butylene terephthalate) (Ny6/PBT) blends. The results reveal the essential role of carboxyl. end groups in the exchange reaction, and allow drawing a detailed mechanism for this reaction. Using Ny6 and PBT samples bearing specific reactive end groups, it was demonstrated that only the carboxyl end groups of PBT and of Ny6 are able to react in the initially biphasic Ny6/PBT blends, so that an outer-inner exchange takes place (Scheme 3). The composition of the copoly(esteramide) obtained at 260degreesC in the exchange of Ny6/PBT shows a higher amount of Ny6 units with respect to the initial blend composition and a high value of the Ny6 average sequence length. However, the composition of the copoly(esteramide) obtained at 280degreesC was instead found to be equal to the feed composition (50/50), with a random distribution of average sequence lengths. The results obtained in the present work can be reconciled within the overall model of exchange reaction occurring through active chain ends.