Solid‐state NMR characterizations on phase structures and molecular dynamics of poly(ethylene‐co‐vinyl acetate)

Solid‐state nuclear magnetic resonance spectroscopy and relaxation measurements, together with DSC, have been used to elucidate the structures and molecular dynamics in poly(ethylene‐co‐vinyl acetate) (EVA). It has been found that besides immobile orthorhombic and monoclinic crystalline phases, the third mobile crystalline phase (possibly the phase) of a considerable amount (36% of total crystalline phases) appears in the EVA samples, which forms during room‐temperature aging as a result of the secondary crystallization and melts at temperature somewhat higher than room temperature. Such a mobile crystalline phase has not only the well‐defined chemical shift of its own, but also has different molecular mobility from the orthorhombic phase. The mobile crystalline phase is characterized by the rapid relaxation of the longitudinal magnetization, which is caused by conventional spin‐lattice relaxation, while the slow relaxation of the longitudinal magnetization occurring in the orthorhombic phase is originated from the chain diffusion. In addition, the amorphous phase also contains two components: an interfacial amorphous phase and a melt‐like amorphous phase. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2864–2879, 2006     

Poly(epichlorohydrin) modified with 3,4,5‐tris(dodecyloxy)benzoate: The structure and dynamics of the aliphatic side chains in the columnar mesophase

We investigated the dynamics and structure of the aliphatic side chains of a randomly grafted copolymer, obtained through the chemical modification of poly(epichlorohydrin) with potassium 3,4,5‐tris(dodecyloxy)benzoate, with solid‐state ¹³C NMR. Below 283 K, the aliphatic chains partially crystallized in an all‐anti conformation. The calorimetric data were compatible with an orthorhombic packing. Below 323 K, the polymer exhibited a columnar mesophase. Spin–lattice relaxation times were determined in this temperature range and at 333 K, that is, in the isotropic phase. In the liquid‐crystalline state, some carbons exhibited a double decay in the spin–lattice relaxation, and this was attributed to presence of the liquid‐crystalline phase. This hypothesis was supported by a conformational analysis performed by molecular modeling. The activation energies of the relaxation processes in the mesophase were also estimated. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2099–2111, 2005     

Tailoring the liquid crystalline property via controlling the generation of dendronized polymers containing azobenzene mesogen

The first‐ and second‐generation dendronized polymers containing azobenzene mesogen were designed and successfully synthesized via free radical polymerization. The chemical structures of the monomers were confirmed by elemental analysis, ¹H NMR, and ¹³C NMR. The molecular characterizations of the polymers were performed with ¹H NMR and gel permeation chromatography. The phase structures and transition behaviors were studied using differential scanning calorimetry, polarized light microscopy, and small‐angle X‐ray scatter experiments. The experiment results revealed that the first‐generation dendronized polymer exhibited liquid crystalline behavior of the conventional side‐chain liquid crystalline polymer with azobenzene mesogen, that is, the polymer exhibited smectic phase structure at lower temperature and nematic phase structure at higher temperature. However, the second‐generation dendronized polymers exhibited more versatile intriguing liquid crystalline structures, namely smectic phase structure at lower temperature and columnar nematic phase structure at higher temperature, and moreover, the phase structure still remained before the decomposition temperature. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1149–1159, 2010     

Promotion of the γ‐phase of polyamide 6 in its nanocomposite with phosphate glass

The effect of tin fluorophosphate‐glass (Pglass) nanoparticles on the polyamide‐6 (PA6) matrix in Pglass/PA6 hybrids has been investigated by ¹³C solid‐state nuclear magnetic resonance (NMR). The crystallinity determined by direct‐polarization ¹³C NMR combined with longitudinal relaxation‐time (T_1C) filtering varied between 31 and 44%. T_1C‐filtered ¹³C spectra with cross polarization clearly showed resonances of both the α‐ and γ‐crystalline phases of PA6, typically at ratios near 45:55, while the similarly processed neat polymer contained only the α‐phase. This suggests that the Pglass promotes the growth of the γ‐crystalline phase. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 857–860, 2008     

Studies on the phase structure of ethylene‐vinyl acetate copolymers by solid‐state 1H and 13C NMR

The phase structure of a series of ethylene‐vinyl acetate copolymers has been investigated by solid‐state wide‐line ¹H NMR and solid‐state high‐resolution ¹³C NMR spectroscopy. Not only the degree of crystallinity but the relative contents of the monoclinic and orthorhombic crystals within the crystalline region varied with the vinyl acetate (VA) content. Biexponential ¹³C NMR spin–lattice relaxation behavior was observed for the crystalline region of all samples. The component with longer ¹³C NMR spin–lattice relaxation time (T₁) was attributed to the internal part of the crystalline region, whereas the component with shorter ¹³C NMR T₁ to the mobile crystalline component was located between the noncrystalline region and the internal part of the crystalline region. The content of the mobile crystalline component relative to the internal part of the crystalline region increased with the VA content, showing that the ¹³C NMR spin–lattice relaxation behavior is closely related to the crystalline structure of the copolymers. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2199–2207, 2002     

Synthesis and characterization of poly(methylmethacrylate)/silica nanocomposites: Study of the interphase by solid‐state NMR and structure/properties relationships

Organic/inorganic nanocomposites were synthesized from poly(methylmethacrylate) (PMMA) and properly modified silica nanoparticles by in situ polymerization. Methacryloylpropyltrimethoxysilane was selected as nanoparticle surface modifier because it is characterized by unsaturated end groups available to radical reactions, making possible to suppose their participation in the acrylic monomer polymerization. As a result of the above hypothesized reactions, a phase constituted by polyacrylic chains grafted onto modified silica surface was isolated. ²⁹Si and ¹³C solid‐state nuclear magnetic resonance experiments permitted to analyze this phase in terms of composition and chain mobility as well as to highlight interaction mechanisms occurring between growing PMMA oligoradicals and functional groups onto silica surface. It was demonstrated that this PMMA grafted onto silica surface acts as an effective coupling agent and assures a good dispersion of nanoparticles as well as a strong nanoparticle/matrix interfacial adhesion. As a result of strong interactions occurring between phases, a significant increase of the glass transition temperature was recorded. Finally, the abrasion resistance of PMMA in the hybrids was significantly improved as a result of a different abrasion propagation mechanism induced by silica particles thus overcoming one of the most serious PMMA drawback. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Annealing‐induced increase of permeability and amorphous‐phase mobility in an ethylene–vinylacetate copolymer

The 50% increased permeability after annealing of semicrystalline poly(ethylene/vinylacetate) containing 3 mol % vinylacetate is linked to increased mobility in the amorphous phase, as identified by line‐narrowing of ¹H wideline nuclear magnetic resonance (NMR) spectra and by reduced cross‐polarization efficiency in ¹³C NMR. Other morphological parameters, such as crystallinity, measured as 30 to 35% by differential scanning calorimetry (DSC) and NMR, are hardly changed by annealing. Small‐angle X‐ray scattering and NMR studies, using spin diffusion as well as T_1ρ and T₁ relaxation, detected only a small increase in crystallite thickness. The annealing‐induced enhancement in segmental mobility in the amorphous regions corresponds to a temperature shift of about 10 K, from which an increase of the motional rate by a factor of 2 is estimated, and which can account for the enhancement in the permeability. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2774–2780, 2001     

Investigation by combined solid‐state NMR and SAXS methods of the morphology and domain size in polystyrene‐b‐polyethylene oxide‐b‐polystyrene triblock copolymers

The microphase structure of a series of polystyrene‐b‐polyethylene oxide‐b‐polystyrene (SEOS) triblock copolymers with different compositions and molecular weights has been studied by solid‐state NMR, DSC, wide and small angle X‐ray scattering (WAXS and SAXS). WAXS and DSC measurements were used to detect the presence of crystalline domains of polyethylene‐oxide (PEO) blocks at room temperature as a function of the copolymer chemical composition. Furthermore, DSC experiments allowed the determination of the melting temperatures of the crystalline part of the PEO blocks. SAXS measurements, performed above and below the melting temperature of the PEO blocks, revealed the formation of periodic structures, but the absence or the weakness of high order reflections peaks did not allow a clear assessment of the morphological structure of the copolymers. This information was inferred by combining the results obtained by SAXS and ¹H NMR spin diffusion experiments, which also provided an estimation of the size of the dispersed phases of the nanostructured copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 55–64, 2010     

Effects of electron irradiation on poly(vinylidene fluoride–trifluoroethylene) copolymers studied by solid‐state nuclear magnetic resonance spectroscopy

The effects of electron irradiation on the molecular chemical structure, conformation, mobility, and phase transition of vinylidene fluoride (VDF) and trifluoroethylene (TrFE) copolymer have been investigated with variable‐temperature, solid‐state ¹⁹F nuclear magnetic resonance (NMR). It has been found that electron irradiation converts all‐trans conformations of both VDF‐rich and TrFE‐containing segments into dynamically mixed trans–gauche conformations accompanied by a simultaneous ferroelectric‐to‐paraelectric (or amorphous) transition. The variable‐temperature ¹⁹F magic‐angle‐spinning spectra results show that the paraelectric phase melts at much lower temperatures in irradiated films than in an unirradiated sample. Moreover, ¹⁹F NMR relaxation data (spin–lattice relaxation times in both the laboratory and rotating frames) reveal that electron irradiation enhances the molecular motion in paraelectric regions, whereas the molecular motion in a high‐temperature amorphous melt (>100 °C) is more constrained in irradiated films. Besides these physical changes, electron irradiation also induces the formation of several CF₃ groups. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1714–1724, 2006     

Crystalline structure of polyamide 12 as revealed by solid‐state 13C NMR and synchrotron WAXS and SAXS

The crystalline structure of polyamide‐12 (PA12) was studied by solid‐state ¹³C nuclear magnetic resonance (NMR) as well as by synchrotron wide‐ and small‐angle X‐ray scattering (WAXS and SAXS). Isotropic and oriented PA12 showed different NMR spectra ascribed to γ‐ and γ′‐crystalline modifications, respectively. On the basis of the position of the first diffraction peak, the isotropic γ‐form and the oriented γ′‐form were shown to be with hexagonal crystalline lattice at room temperature. When heated, the two PA12 polymorphs demonstrated different behaviors. Above 140 °C, the isotropic γ‐PA12 partially transformed into α‐modification. No such transition was observed with the oriented γ′‐PA12 phase even after annealing at temperatures close to melting. A γ′–γ transition was observed here only after isotropization by melting point. Various structural parameters were extracted from the WAXS and SAXS patterns and analyzed as a function of temperature and orientation: the degree of crystallinity, the d‐spacings, the Bragg's long spacings, the average thicknesses of the crystalline (l_c) and amorphous (l_a) phases, and the linear crystallinity x_cl within the lamellar stacks. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3720–3733, 2005     

Confined crystallization behaviors in polyethylene/silica nanocomposites: Synergetic effects of interfacial interactions and filler network

The confinement effects introduced by nanoparticles have been reported to influence the phase behaviors thus the properties of polymer nanocomposites. In this study, molecular dynamics and crystallization behaviors of polyethylene (PE) composited with three types of silica (SiO₂) nanoparticles, namely unmodified SiO₂, hydrophobically modified SiO₂, SiO₂‐APTES (3‐aminopropyltriethoxysilane) and SiO₂‐PTES (n‐propyltriethoxysilane), were systematically investigated via a combination of DSC, XRD and ¹H solid‐state NMR measurements. The suppressions in crystallization and chain mobilities of PE rank in the order of unmodified SiO₂ < SiO₂‐APTES < SiO₂‐PTES due to the increasing interfacial interactions between PE and SiO₂ nanoparticles. Additionally, independent of polymer–nanoparticle interactions, a silica network forms for all three kinds of nanocomposites when SiO₂ content reaches 83 wt %. The mobilities of polymer chains are severely restricted by such a percolated network structure, leading to a turning point in the crystallization ability of nanocomposites and a new crystallization peak at 45 °C lower than that of pure PE. The synergetic effects of interfacial interactions and filler network on polymer crystallization have been thoroughly studied in this work, which will provide guidance on modifying and designing nanocomposites with controlled properties. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 498–505     

Design,synthesis, and characterization of a combined main‐chain/side‐chain liquid crystalline polymer based on mesogen‐jacketed liquid crystal polymer via atom transfer radical polymerization

A novel combined main‐chain/side‐chain liquid crystalline polymer based on mesogen‐jacketed liquid crystal polymers (MJLCPs) containing two biphenyls per mesogenic core of MJLCPs main chain, poly(2,5‐bis{[6‐(4‐butoxy‐4′‐oxy‐biphenyl)hexyl]oxycarbonyl}styrene) (P1–P8) was successfully synthesized via atom transfer radical polymerization (ATRP). The chemical structure of the monomer was confirmed by elemental analysis, ¹H NMR, and ¹³C NMR. The molecular characterizations of the polymer with different molecular weights (P1–P8) were performed with ¹H NMR, gel permeation chromatography (GPC), and thermogravimetric analysis (TGA). Their phase transitions and liquid‐crystalline behaviors of the polymers were investigated by differential scanning calorimetry (DSC) and polarized optical microscope (POM). We found that the polymers P1–P8 exhibited similar behavior with three different liquid crystalline phases upon heating to or cooling in addition to isotropic state, which should be related to the complex liquid crystal property of the side‐chain and the main‐chain. Moreover, the transition temperatures of liquid crystalline phases of P1–P8 are found to be dependent on the molecular weight. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7310–7320, 2008     

Complementarity of universal calibration SEC and 13C NMR in determining the branching state of polyethylene

The quantitation of long‐chain branching (LCB) and short‐chain branching (SCB) in polyethylene (PE) was accomplished with a combination of carbon nuclear magnetic resonance (¹³C NMR) spectroscopy and size exclusion chromatography (SEC) with universal calibration. We demonstrate how the spectroscopic and chromatographic techniques can supplement each other, as neither is capable individually of completely describing the molecular architecture imparted by the various types of branching. The essential lack of impact of SCB on the hydrodynamic volume imposes a limit on SEC for determining this type of branching, whereas highly effective LCB in the PE molecule may not offer a statistically large enough amount of long chains for accurate determination by NMR. A variety of examples are given for PE, showcasing the advantages and shortcomings of each analytical method and their complementarity. Additionally, the importance of choosing an appropriate linear standard and viscosity shielding ratio (ϵ) for the Zimm–Stockmayer branching calculations employed for analyzing SEC data is emphasized with an examination of the effect on the results of using a branched standard and various ϵ values. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 3120–3135, 2000     

Synthesis of amorphous aliphatic polyester‐ether homo‐ and copolymers by radical polymerization of ketene acetals

Radical ring‐opening polymerization has been efficiently used to copolymerize 2‐methylene‐1,3,6‐trioxocane (MTC) and 2‐methylene‐1,3‐dioxepane (MDO). The cyclic ketene acetal MTC was first synthesized and homopolymerized at different temperatures using either 2,2‐azobisisobutyronitrile or dicumyl peroxide as initiator. The polymerization mechanism was not temperature‐dependent, and the polymerization proceeded with 100% ring‐opening at all the temperatures evaluated. The structures of MTC and PMTC were verified by ¹H‐nuclear magnetic resonance (NMR) and ¹³C‐NMR spectroscopies. A number‐average molecular weight of 6500 was obtained after 2 days at 70 °C in bulk, which was somewhat higher than the theoretical molecular weight. A significant amount of branching was detected from the high polydispersity index as well as the glass‐transition temperatures. The polyester‐ether was then successfully obtained by copolymerization of MTC with MDO. Different feed ratios and temperatures were used to map the reaction, and the copolymers were characterized by NMR, size exclusion chromatography, and differential scanning calorimetry. The amount of MTC within the polymer was independent of the feed ratio and always higher than the amount of MDO. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Effect of the repeated unit length of guest polymers on the molecular motion of polymer blends within a miscible window

The effect of the repeated unit length on the substantially increasing molecular motion and entropy change (?TΔS_m) of polymer blends was investigated with solid‐state ¹³C NMR and differential scanning calorimetry within a miscible window. The hydrogen‐bonding strength, from the formation of the phenolic–polyester interaction, was not high enough to overcome the breaking‐off of the self‐association of the phenolic. With respect to the increasing repeated unit length, the polyester resonance intensity of the solid‐state ¹³C NMR spectra was weakened because of the reduction in the cross‐polarization efficiency in highly mobile samples. The glass‐transition temperature of the blend and the proton spin–lattice relaxation time from NMR experiments were also reduced. The effect of the reduced hydrogen‐bonding strength on blending brought about a tendency of higher entropy (?TΔS_m) and higher molecular mobility of the blend. Accordingly, poly(decamethylene adipate) possessed the longest repeated unit length and exhibited the most mobile one in this phenolic/polyester blend family. The molecular segmental motion and entropy progressively increased while the repeated unit length of the guest polymers increased within a miscible window. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 679–686, 2003     

On the anionic homo‐ and copolymerization of ethyl‐ and butyl‐2‐cyanoacrylates

Ethyl‐(ECA) and butyl‐2‐cyanoacrylate (BCA) monomers of high purity and acidic stabilization were synthesized and anionically polymerized to homo‐ and copolymers in two different ways: by piperidine‐catalyzed bulk polymerization leading to transparent, brittle films (method A) and by polymerization in aqueous medium in the presence of sodium bicarbonate to obtain white powders (Method B). The molecular structure of the synthesized monomers, homopolymers and copolymers were corroborated by spectral methods. The polymers were studied further by thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), size exclusion chromatography (SEC) and proton nuclear magnetic resonance (¹H NMR). Controlling the composition of the monomer feed and the way the polymerization was performed, it was possible to obtain phase separated or homogeneous cyanoacrylate copolymers with glass transitions varying between the T_g of polyECA and that of polyBCA. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5142–5156, 2008     

Characterization of signals in the solution 1H NMR spectrum of poly(isobutylene‐co‐p‐methylstyrene) and their utility

Poly(isobutylene‐co‐p‐methylstyrene) is an important precursor to Exxpro™ elastomers. A previous report detailed the characterization of both the proton and the carbon NMR spectra of the copolymer. 1 However, several resonances in the proton NMR spectrum of the copolymer were not assigned. Specifically, the proton methine resonance of the BSB triad sequence is now identified and used to calculate BSB triad contribution to the copolymer microstructure. This report describes the assignment of this resonance and other resonances associated with microstructural sequence distribution around p‐methylstyrene. The proton NMR signals of interest resonate at 2.8 ppm and 2.5 ppm in a typical spectrum for poly(isobutylene‐co‐p‐methylstyrene). The nature of these resonances were determined by preparation and characterization of specifically deuterated poly(isobutylene‐co‐p‐methylstyrene)s employing both one and two dimensional NMR techniques. The 2.8 ppm signal is assigned as the methine proton of a p‐methylstyrene incorporated between two isobutylene units (the BSB triad). The signal at 2.5 ppm is assigned to the meso‐BSS triad. Determination of these resonances allows for rapid evaluation of isolated p‐methylstyrene units (BSB triads) present in the copolymer using only ¹H NMR. The utility of this technique is demonstrated by comparing BSB triad values determined by ¹H and ¹³C NMR analysis. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1680–1686, 2000     

One‐step synthesis of hyperbranched polyethylene macroinitiator and its block copolymers with methyl methacrylate or styrene via ATRP

Block copolymers of hyperbranched polyethylene (PE) and linear polystyrene (PS) or poly(methyl methacrylate) (PMMA) were synthesized via atom transfer radical polymerization (ATRP) with hyperbranched PE macroinitiators. The PE macroinitiators were synthesized through a “living” polymerization of ethylene catalyzed with a Pd‐diimine catalyst and end‐capped with 4‐chloromethyl styrene as a chain quenching agent in one step. The macroinitiator and block copolymer samples were characterized by gel permeation chromatography, ¹H and ¹³C NMR, and differential scanning calorimetry. The hyperbranched PE chains had narrow molecular weight distribution and contained a single terminal benzyl chloride per chain. Both hyperbranched PE and linear PS or PMMA blocks had well‐controlled molecular weights. Slow initiation was observed in ATRP because of steric effect of hyperbranched structures, resulting in slightly broad polydispersity index in the block copolymers. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3024–3032, 2010     

Spectroscopic and photopolymerization studies of benzyl methacrylate/poly(benzyl methacrylate) two‐component system

The influence of the viscosity of a two‐component system on its molecular dynamics (on the basis of hypersonic wave velocity and attenuation coefficient) and photopolymerization kinetics was studied. The system investigated represented the solution of poly(benzyl methacrylate), PBzMA (MW = 70000) in its monomer, benzyl methacrylate (BzMA). The viscosity of the system was varied by adding various amounts of the polymer to the monomer (10–50 wt %). The molecular dynamics in the neat BzMA was studied by the proton Nuclear Magnetic Resonance (NMR) spin‐lattice relaxation time measurements and the wide‐line ¹H NMR spectroscopy in a wide range of temperature. Information on the local dynamics in liquid BzMA above its melting temperature was gained from the high‐resolution ¹H and ¹³C NMR spectra. The hypersonic wave velocity and the attenuation coefficient were investigated in the appropriate temperature range related to a viscoelastic relaxation process by the Brillouin light scattering method. The kinetic measurements have demonstrated that the photopolymerization rate rapidly increases and the monomer conversion decreases with increasing polymer‐to‐monomer ratio; this effect has been noted in the whole range of polymer concentration and reaction temperature studied. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1336–1348, 2010     

Solid-State 13C-NMR detection of the isotropic carbonyl line shape in blends of poly(vinylphenol) with main-chain polyesters

The solid-state NMR isotropic line shape of the carbonyl ¹³C resonance is useful as a qualitative diagnostic probe of the polyester component′s morphology and molecular mobility in partially miscible blends with poly(vinylphenol), PVPh. The main-chain polyesters chosen for investigation in this study are poly(ethylene succinate), poly(ethylene adipate), poly(butylene adipate), and poly(caprolactone). A crystalline phase exists for polyester-rich mixtures in all cases. Verification of this claim is provided by DSC endothermic tran-sitions that map out melting point depression in the temperature-composition phase dia-grams. The carbonyl ¹³C-NMR signal in the crystalline domains exhibits a full width at half height of 1–2 ppm when the glass transition temperature of the blends is below the temperature of the NMR experiment. In all cases, a single concentration-dependent glass-transition temperature is measured by DSC, which increases monotonically from below ambient for polyester-rich blends to well above ambient for blends that are rich in poly(vinylphenol). When the concentration of the amorphous proton donor PVPh is suf-ficient to thwart crystallization of the polyester and increase the glass transition temperature of the blends above the temperature of the NMR experiment, the line width of the carbonyl resonance increases three- to fourfold to ca. 5–6 ppm. When the blends are completely amorphous and T_g is above ambient, the polyester carbonyl ¹³C line shape reveals at least two morphologically inequivalent microenvironments. A partially resolved carbonyl signal in rigid amorphous blends is (a) identified at higher chemical shift relative to the crystalline component, and (b) attributed to hydrogen bonding in the amorphous phase. This inter-action-sensitive hydrogen-bonded carbonyl signal accounts for an increasing fraction of the overall NMR absorption envelope of the carbonyl carbon site when the polyester is saturated with PVPh. The main-chain polyesters were chosen to probe the effect of chemical structure of the proton acceptor on the potential for hydrogen-bond formation. Aliphatic CH₂ spacers between the carbonyl groups dilute the concentration of interacting sites, and the dependence of the carbonyl ¹³C-NMR line shape on blend concentration reveals unique spectroscopic behavior in each of the four blend systems investigated. © 1993 John Wiley & Sons, Inc.