Cyclodi(ethylene succinate) (C2) easily reacts with poly(ethylene terephthalate) (PET) in the melt leading to the formation of high molar mass PET‐Poly(ethylene succinate) copolymers (PET‐PES). ...Copolyesters with a PET/C2 starting mass ratio of 90/10, 80/20, 70/30 and 50/50 were synthesized and characterized by 1H NMR and MALDI‐TOF MS. The 50/50 copolyester was almost random, while copolyesters with higher ethylene terephthalate contents exhibited some block copolymer character. MALDI‐TOF MS/SEC off‐line coupling was used to determine copolyester absolute average molar masses. The results indicate that the conventional SEC polystyrene calibration strongly overestimates copolyester molar masses. The melting temperatures and crystallinity of the 90/10, 80/20 and 70/30 copolyesters were significantly higher than those of comparable PET‐aliphatic polyester copolymers.
Opisan je novi sustav nomenklature (imenovanja) na osnovi podrijetla za polimere koji su kemijski modificirani. U tu je svrhu u ime polimera uvedena poveznica -mod-, npr. poli(A)-mod-(B). Sustav se ...primjenjuje u skladu s nomenklaturom polimera na osnovi podrijetla, ali predviđa, kada je to neizbježno, i imenovanje polimera na osnovi strukture. Sustav uključuje: (1) modifikaciju konstitucijske jedinice u drugu jedinicu poznate strukture; (2) općenitiju modifikaciju konstitucijske jedinice kojom nastaje bilo koja od više mogućih struktura. Uveden je i novi simbol, ~>, za uporabu pri grafičkom prikazivanju strukture modificiranih polimera.
Expressions for the degree of randomness, B, and for the number- and weight-average block lengths of condensation copolymers containing both symmetrical (AA + BB) and unsymmetrical (AB) monomer units ...are established through an approach based on functional group probabilities. Several parameters introduced in literature to characterize randomness in AA + BB condensation copolymers are also calculated using this approach and compared to B, showing that they are simple linear or rational functions of B. A method for calculating functional group probabilities from the dyad and triad number-fractions determined by NMR spectroscopy is described for poly(ethylene terephthalate)-poly(ε-caprolactone) copolyesters. This method obviously applies to any AA + BB + AB polycondensation and is easily generalizable to other types of condensation copolymers.
Hyperbranched aliphatic polyesters of 2,2′‐bis‐(hydroxymethyl) propanoic acid and hyperbranched aliphatic polyamides obtained from new carboxy‐ and amino‐functionalized caprolactams were studied by ...NMR spectroscopy and MALDI‐TOF mass spectrometry. Ring‐chain equilibria taking place through intramolecular hydroxy‐ester, carboxy‐amide or amine‐amide interchanges and leading to the formation of cyclic branches or end‐groups were found to exert a predominant influence on the molar mass of these hyperbranched polymers. A number of intra‐ or intermolecular side reactions, such as the formation of ethers in polyesters and the formation of anhydrides, imides, amidines and secondary amines in polyamides were also detected and resulted in polymer crosslinking on prolonged heating. The existence of such ring‐chain equilibria and side‐reactions make the control of hyperbranched polymer structure much more difficult than generally accepted.
ε-Caprolactone (CL) was reacted with PGA oligomers in ionic liquids in the presence of Ti(OBu)
, both ring-opening polymerization initiator and polyesterification catalyst.
H and
C NMR studies showed ...that the fast polymerization of CL was followed by simultaneous slow polyesterification and ester-interchange reactions leading to random PGA/CL copolyesters after 6 h reaction. The nature of the catalyst and the ionic liquid did not influence much reaction rate. Hydroxyacetyl end-groups appeared to be much less reactive than the corresponding hydroxycaproyl end-groups, which were consumed at the beginning of reaction. The 50/50 and 60/40 oxyacetyl (G)/oxycaproyl (L) (mass-%) copolyesters were amorphous, while copolyesters containing larger amounts of G units were semi-crystalline. The variations of the T
of all copolyesters versus composition follow the Flory-Fox law.
Abstract
Summary:
Copolyesters containing aliphatic units in the main chain were obtained by reacting high molar mass poly(ethylene terephthalate) (PET) with
ε
‐caprolactone or
δ
‐valerolactone at ...high temperature in the bulk.
γ
‐Butyrolactone did not react in these conditions. Thermal properties were studied by DSC and TGA, and structural characterizations were carried out by
1
H NMR spectroscopy and SEC/MALDI‐TOF mass spectrometry off‐line coupling. These techniques demonstrate the insertion of lactone units in PET chains. Linear species with hydroxy, carboxy and vinyl ester end‐groups were clearly identified in the mass spectra, together with cyclic copolymer species. Narrow‐distribution copolyester SEC fractions were characterized by MALDI‐TOF mass spectrometry and used to establish a SEC calibration curve against absolute molar masses. The results indicate that the conventional polystyrene SEC calibration strongly overestimates copolyester molar masses. The degree of randomness of these copolyesters, determined by
1
H NMR, shows that chain microstructure presents some block‐copolymer character. The thermal properties of the copolyesters are also discussed.
Reaction between PET and
γ
‐butyrolactone (
x
= 3),
δ
‐valerolactone (
x
= 4), or
ε
‐caprolactone (
x
= 5).
magnified image
Reaction between PET and
γ
‐butyrolactone (
x
= 3),
δ
‐valerolactone (
x
= 4), or
ε
‐caprolactone (
x
= 5).
Copolyesters containing aliphatic units in the main chain were obtained by reacting high molar mass poly(ethylene terephthalate) (PET) with ε‐caprolactone or δ‐valerolactone at high temperature in ...the bulk. γ‐Butyrolactone did not react in these conditions. Thermal properties were studied by DSC and TGA, and structural characterizations were carried out by 1H NMR spectroscopy and SEC/MALDI‐TOF mass spectrometry off‐line coupling. These techniques demonstrate the insertion of lactone units in PET chains. Linear species with hydroxy, carboxy and vinyl ester end‐groups were clearly identified in the mass spectra, together with cyclic copolymer species. Narrow‐distribution copolyester SEC fractions were characterized by MALDI‐TOF mass spectrometry and used to establish a SEC calibration curve against absolute molar masses. The results indicate that the conventional polystyrene SEC calibration strongly overestimates copolyester molar masses. The degree of randomness of these copolyesters, determined by 1H NMR, shows that chain microstructure presents some block‐copolymer character. The thermal properties of the copolyesters are also discussed.
Reaction between PET and γ‐butyrolactone (x = 3), δ‐valerolactone (x = 4), or ε‐caprolactone (x = 5).
Bis(5(4H)oxazolinones) derived from naturally occurring α‐amino acids were reacted with amine‐terminated polyethers and polyamides in the bulk at 175–200°C. Model reactions were also carried out ...using primary alkylamines. The reactions were studied by means of SEC, and 1H and 13C NMR, and the resulting polymers were characterized by DSC and TGA. The chain‐coupling reaction is extremely fast and yields high molar mass copolymers containing peptide linkages in less than 5 min. The NMR spectra of model compounds and polymers were fully assigned, showing that the oxazolinone/amine polyaddition reaction proceeds in the expected way, without any noticeable side reaction. The polymers exhibit lower crystallinity, higher Tg and a melting temperature close to or lower than that of the starting oligomers.
The bulk chain‐coupling reactions between hydroxy‐terminated poly(oxytetramethylene), poly(oxyethylene), or poly(ε‐caprolactone) and several bis(4‐monosubstituted‐5(4H)oxazolinones) were studied. The ...polyaddition reaction proceeds rapidly and without side reactions when a catalytic amount of Ti(OBu)4 is used in the case of poly(oxytetramethylene) or poly(ε‐caprolactone). On the other hand, the efficiency of the chain extension was much lower in the case of poly(oxyethylene). An explanation involving the coordination of poly(oxyethylene) oxygen atoms at the active sites of tetrabutoxytitanium is put forward. High molar mass block copolymers were synthesized by the chain‐coupling reaction of mixtures of α,ω‐dihydroxy‐poly(oxytetramethylene) and ‐poly(ε‐caprolactone) with bis(oxazolinones). The differential scanning calorimetry (DSC) study of the block copolymers revealed the existence of a microphase separation between the two blocks when the starting polymers have Mn ≥ 1000. For lower molar mass polymers amorphous products were obtained.
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