Comparison Of Poly Research Articles

Comparison of poly(ε-caprolactone) chain lengths of poly(ε-caprolactone)-co-d-α-tocopheryl-poly(ethylene glycol) 1000 succinate nanoparticles for enhancement of quercetin delivery to SKBR3 breast cancer cells

This study aimed to investigate the effect of the different hydrophobic chain lengths of poly(ε-caprolactone)-co-d-α-tocopheryl polyethylene glycol 1000 succinate (P(CL)-TPGS) copolymers on the nanoparticle properties and delivery efficiency of quercetin to SKBR3 breast cancer cells. The 5:1, 10:1 and 20:1 P(CL)-TPGS copolymers were fabricated and found to be composed of 25.0%, 45.2% and 66.8% of hydrophobic P(CL) chains with respect to the polymer chain, respectively. The DSC measurement indicated the microphase separation of P(CL) and TPGS segments. The crystallization of P(CL) segment occurred when the P(CL) chain was higher than 25% due to the restricted mobility of P(CL) by TPGS. The longer P(CL) chain had the higher crystallinity while decreasing the crystallinity of TPGS segment. The increasing P(CL) chain length increased the particle size of P(CL)-TPGS nanoparticles from 20 to 205nm and enhanced the loading capacity of quercetin due to the more hydrophobicity of the nanoparticle core. The release of quercetin was retarded by an increase in P(CL) chain length associated with the increasing hydrophobicity and crystallinity of P(CL)-TPGS copolymers. The P(CL)-TPGS nanoparticles potentiated the toxicity of quercetin to SKBR3 cells by at least 2.9 times compared to the quercetin solution. The cellular uptake of P(CL)-TPGS nanoparticles by SKBR3 cells occurred through cholesterol-dependent endocytosis. The 10:1 P(CL)-TPGS nanoparticles showed the highest toxicity and uptake efficiency and could be potentially used for the delivery of quercetin to breast cancer cells.

Nanovoid formation and mechanics: a comparison of poly(dicyclopentadiene) and epoxy networks from molecular dynamics simulations.

Protective equipment in civilian and military applications requires the use of polymer materials that are both stiff and tough over a wide range of strain rates. However, typical structural materials, like tightly cross-linked epoxies, are very brittle. Recent experiments demonstrated that cross-linked poly(dicyclopentadiene) (pDCPD) networks can circumvent this trade-off by providing structural properties such as a high glass transition temperature and glassy modulus, while simultaneously exhibiting excellent toughness and high-rate impact resistance. The greater performance of pDCPD was attributed to more facile plastic deformation and nano-scale void formation, but the chemical and structural mechanisms underlying this response were not clear. Here, we use atomistic molecular dynamics to compare the molecular- and chain-level properties of pDCPD and epoxy networks undergoing high strain rate deformation. We quantify the tensile modulus and yield strength of the networks as well as the prevalence and characteristics of nanovoids that form during deformation. Networks of similar molecular weight between cross-links are compared. Two key molecular-level properties are identified - monomer flexibility and polar chemistry - that influence the behavior of the networks. Increasing monomer flexibility reduces the modulus and yield strength, while strong non-covalent interactions (e.g., hydrogen bonds) that accompany polar moieties provide higher modulus and yield strength. The lack of strong non-covalent interactions in pDCPD was found to account for its lower modulus and yield strength compared to the epoxies. We examine the molecular-level properties of nanovoids, such as shape, alignment, and local stress distribution, as well as the local chemical environment, finding that nanovoid formation and growth are increased by the monomer rigidity but decreased by polar chemistry. As a result, the pDCPD network, which has a stiff chain backbone with nonpolar alkane chemistry, exhibits more and larger nanovoids that grow more readily during deformation, which could account for the higher toughness and more ductile behavior observed in pDCPD.

The synthesis and comparison of poly(methacrylic acid)–poly(ε-caprolactone) block copolymers with and without symmetrical disulfide linkages in the center for enhanced cellular uptake

A self-assembled poly(methacrylic acid)–poly(ε-caprolactone) block copolymer with a disulfide linkage, PMAA-b-PCL-SS-PCL-b-PMAA, was synthesized for enhanced cellular uptake due to a reduction response to GSH and pH-sensitive characteristics.

Formation and comparison of poly(l-lactide)-guided polyaniline morphology via normal and phase alternated interfacial polymerization

Taking the poly(l-lactide), PLLA, as a guider to form polyanilines, PANI, via interfacial polymerization, we prepared two PANI samples. The one is the normal interfacial polymerization performed by taking the APS formed aqueous phase, AP, as the top phase and the ANI and PLA formed oil phase, OP, as the bottom phase; and the another was the phase alternated interfacial polymerization performed by taking the OP as the top phase and the AP as the bottom phase. FESEM images showed that the morphology of PLLA-guided PANI was strongly influenced by these two methods because the normal process formed a vertebra-like morphology with four round leaves in the cross-section, and the phase alternated process formed smooth and uniform microfibers. This difference was considered due to the phase alternation-induced different oxidation processes.

Temperature‐Induced Phase Separation and Hydration in Aqueous Polymer Solutions Studied by NMR and IR Spectroscopy: Comparison of Poly(N‐vinylcaprolactam) and Acrylamide‐Based Polymers

SummaryUsing NMR and IR spectroscopy we compared the LCST behaviour of two types of thermoresponsive polymer systems, poly(N‐vinylcaprolactam) (PVCL) and acrylamide‐based polymers in aqueous solutions. We confirmed that during phase separation both PVCL and poly(N‐isopropylmethacrylamide) (PNIPMAm) chains undergo coil‐globule transition. At the same time some important differences were found for PVCL in comparison with PNIPMAm and poly(N‐isopropylacrylamide) (PNIPAm), especially a much lower level of dehydration of PVCL segments at temperatures above the phase transition. We assume that the origin of these differences can be in different structure of respective monomer units. From time dependences of ATR FTIR spectra it follows that the low degree of dehydration of PVCL segments is not changed with time. Small increase in the wavenumbers of the Amide I components of the hydrated PVCL carbonyl groups with time indicates that water released from PVCL mesoglobules with time, as revealed from NMR T2 measurements, might be mainly indirectly bound water.

Comments on the Implementation of a Simple Peak Capacity Optimization Procedure and Comparison of Poly(styrene–divinylbenzene) and RP-18 Silica Monolithic Capillary Columns of 5-cm for the Analysis of Protein Digests

For the analysis of protein digests, the peak capacity in reversed-phase liquid chromatography is of paramount importance. A univariate method to maximize the peak capacity as developed by Wang et al. (Anal Chem 78:3406–3416, 20) has been applied and tested for a monolithic RP-18 silica capillary column. In their method, using model peptides representing a bovine serum albumin digest, the gradient time and temperature are kept constant while the flow rate and eluent strength are varied. Despite our criticism on the fixed starting conditions, a long gradient time leading to an unnecessary long analysis time and a high temperature leading to possible degradation products in the chromatogram, and the peak capacity as the only optimization parameter this fast and simple optimization strategy turns out to be applicable to capillary monolithic columns. Furthermore, the influence of the peak capacity on a second optimization parameter, the MS protein identification score, is examined. The procedure is also used to enhance the performance of two popular types of monolithic capillary LC columns (silica-C18 and poly(styrene–divinylbenzene)) of the same length for the analysis of protein digests. Comparison of both columns show that the calculated chromatographic parameters, like productivity and peak capacity, and identification score for both columns are about the same. For a more complicated nine-protein digest the performance of the silica monolith is slightly better.

Fabrication and I-V Characterization with Monochromatic Light of Multilayer Poly(3-hexylthiophene)-CNT/C60 Thin Films on ITO Glass Substrate

Multilayer poly (3-hexylthiophene)-CNT/C60 thin films on ITO glass substrate was fabricated regarding to the function of each layer. Poly (3-hexylthiophene) (P3HT) is used as a donor layer and fullerene (C60) is used as an acceptor layer of the device. The carbon-nanotube (CNT) is homogeneously mixed in the donor layer to increase charge transportability. The structures of poly (3-hexylthiophene), poly (3-hexylthiophene)-CNT were fabricated in comparison of poly (3-hexylthiophene)-CNT/C60 thin films. The P3HT-CNT bulk heterojunction was deposited on ITO glass substrate by spin coating technique and then the C60 thin film was deposited on the P3HT by thermal evaporating technique. The I-V characteristic of ITO/P3HT-CNT/Al and ITO/P3HT-CNT/C60/Al were investigated in the monochromatic light. The result showed that the ITO/P3HT-CNT/Al structures respond with red and green light, and the ITO/P3HT-CNT/C60/Al structure responds with blue light. The UV absorption was measured and the result was consistence with the I-V characterization.

Poly(vinylalkanamide)s as Kinetic Hydrate Inhibitors: Comparison of Poly(N-vinylisobutyramide) with Poly(N-isopropylacrylamide)

Kinetic hydrate inhibitors (KHIs) are water-soluble polymers that have been used for almost 20 years as a method to prevent the formation of gas hydrate plugs. Most classes of KHI polymers contain amide groups. We have now found a simple route to synthesize poly(N-vinylalkanamide)s (PVamides) from polyvinylamine. In this paper, we present results on the KHI performance of PVamides with varying alkyl chain lengths in the side group. This has been performed in tests with a structure-II-forming synthetic natural gas in high-pressure rocker cells and on tetrahydrofuran (THF) structure II hydrate crystal growth. The KHI performance of poly(N-isopropylacrylamide)s (PNIPAMs) and poly(N-vinylisobutyramide)s (PNVIBAs) at varying molecular weights was also compared, because these two polymers differ only in the orientation of the amide group.

Electrochemical Generation and Spectroscopic Characterization of Charge Carriers within Isolated Planar Polythiophene

In order to unveil the nature of charge carriers in a doped polythiophene, a sterically isolated polythiophenene, poly(1EDOT), was electrochemically synthesized on electrodes. Generation of charge carriers was induced upon controlled electrochemical doping and investigated through various spectroscopic methods; the charge carriers were identified based on spin concentration (ESR spectra), aromatic character (Raman spectra), and electronic transition (UV–vis–NIR absorption spectra) of the polythiophene. Peculiarity of this study lies in the fact that the electrochemistry of the poly(1EDOT) reflects the p-doping process of a single polythiophene wire because interwire interaction (i.e., π–π stacking) is effectively prevented; therefore, the results should be essential and informative to understand polythiophene-based materials and devices. Upon electrochemical doping, ESR active polarons were generated. Further doping concentrated the polarons, which led to the formation of polaron pairs. Eventually, the polaron pairs merged into bipolarons at the doping level of about 30–35%. Such a transformation of charge carriers under different doping levels has been extrapolated from studies using oligomeric model compounds. To the best of our knowledge, this is the first example addressing the nature of the charge carriers generated in a single polythiophene wire by exploiting the unique structure of the isolated polythiophene. Importantly, the comparison of poly(1EDOT) with common polythiophenes such as poly(3,4-ethylenedioxythiophene) (i.e., polyEDOT) implied that π–π stacking strongly affects the generation and stability of charge carriers. Furthermore, we found that the polaron pair plays an important role in charge hopping transport in the conduction mechanism.

Amphiphilic Polybetaines: The Effect of Side-Chain Hydrophobicity on Protein Adsorption

Novel amphiphilic polybetaines were synthesized and used as the base material for nonfouling coatings. The amphiphilicity of these polybetaines was systematically tuned by coupling chains of increasing hydrophobicity to the zwitterionic functionality side at the repeat unit level. An oligoethylene glycol (OEG) moiety was selected to yield the most hydrophilic coating, while octyl (C(8)) and fluorinated (F) groups were used to impart lipophilicity and lipophobicity to the coatings, respectively. This unique design allowed us to investigate the effect of the lipophilicity/lipophobicity of the side chain on the nonfouling properties of these zwitterionic systems. Adsorption studies, performed using six different proteins, showed that the fluorinated polybetaine, Poly[NFZI-co-NSi], resisted nonspecific adsorption as effectively as, and in some cases even better than, the most hydrophilic Poly[NOEGZI-co-NSi] coating. The comparison of Poly[NFZI-co-NSi] to its noncharged analog demonstrated the essential nature of the zwitterionic functionality in imparting nonfouling character to the coating.

Thermoresponsive Poly(2‐oxazine)s

The monomers 2-methyl-2-oxazine (MeOZI), 2-ethyl-2-oxazine (EtOZI), and 2-n-propyl-2-oxazine (nPropOZI) were synthesized and polymerized via the living cationic ring-opening polymerization (CROP) under microwave-assisted conditions. pEtOZI and pnPropOZI were found to be thermoresponsive, exhibiting LCST behavior in water and their cloud point temperatures (T(CP)) are lower than for poly(2-oxazoline)s with similar side chains. However, comparison of poly(2-oxazine) and poly(2-oxazoline)s isomers reveals that poly(2-oxazine)s are more water soluble, indicating that the side chain has a stronger impact on polymer solubility than the main chain. In conclusion, variations of both the side chains and the main chains of the poly(cyclic imino ether)s resulted in a series of distinct homopolymers with tunable T(CP).

A Chiroptical Photoswitchable DNA Complex

The interesting structural, electronic, and optical properties of DNA provide fascinating opportunities for developing nanoscale smart materials by integrating DNA with opto-electronic components. In this article we demonstrate the electrostatic binding of an amine-terminated dithienylethene (DET) molecular switch to double-stranded synthetic polynucleotides. The DET switch can undergo photochemical ring-closure and opening reactions. Circular dichroism (CD) and UV-vis spectroscopy show that both the open, 1o, and the closed, 1c, forms of the switch bind to DNA. Upon addition of DNA to a solution of 1o or 1c, the UV-vis spectrum displays a hypochromic effect, indicative of an interaction between the switch and the DNA. The chirality of the DNA double-helix is transmitted to the switching unit which displays a well-defined CD signal upon supramolecular complexation to the DNA. Additionally, the CD signal of the DNA attenuates, demonstrating that both components of the complex mutually influence each other's structure; the DNA induces chirality in the switch, and the switch modifies the structure of the DNA. Modulation of the chiroptical properties of the complex is achieved by photochemically switching the DET between its ring open and closed isomers. A pH dependence study of the binding shows that when the pH is increased the switches lose their binding ability, indicating that electrostatic interactions between protonated amines and the negatively charged phosphate backbone are the dominant driving force for binding to the DNA. A comparison of poly(deoxyguanylic-deoxycytidylic) acid [poly(dGdC)(2)] polynucleotides with poly(deoxyadenylic-deoxythymidylic) acid [poly(dAdT)(2)] shows distinct differences in the CD spectra of the complexes.

Comparison of the structure-property relationships for PTT and PET fibers spun at various take-up speeds

A comparison of poly(trimethylene terephthalate)(PTT) and poly(ethlene terephthalate)(PET) fibers spun at various take-up speeds was presented. Fiber characterization included tensile and thermal properties, optical birefringence, density, sonic modulus, boil-off shrinkage, and wide-angle X-ray diffraction. The phenomenon of stress-induced crystallization was inferred from the X-ray diffraction diagrams for fibers spun with take-up speeds over 4000 m/min. The tenacity and elongation of PTT and PET fiber showed typical results, but the initial modulus of PTT fiber was nearly unchanged over the entire take-up speed range (2000–7000 m/min), whereas that of PET, as expected, increased monotonically with increasing take-up speed. This divergent behavior could be explained by the different molecular deformations in the c-axis as determined from X-ray diffraction patterns. The fiber crystallinity, density, and heat of fusion of both polymers increased with take-up speed. The boil-off shrinkage decreased with increasing take-up speed. The optical birefringence of the two fiber types showed a maximum level at a take-up speed of ca. 5000 m/min. The melting temperature behavior of PTT fiber was different from that of PET fibers. It was found that PTT is less sensitive to stress induced changes at high spinning speeds than is PET.

Positive cooperative mechanistic binding of proteins at low concentrations: A comparison of poly (sodium N-undecanoyl sulfate) and sodium dodecyl sulfate

The interactions of the negatively charged achiral molecular micelle, poly (sodium N-undecanoyl sulfate) (poly-SUS), with four different proteins using intrinsic and extrinsic fluorescence spectroscopic probes, are studied. A comparison of poly-SUS with the conventional surfactant, sodium dodecyl sulfate (SDS), and the monomeric species, SUS, is also reported. In this work, we observed that poly-SUS preferentially binds to acidic proteins, exhibiting positive cooperativity at concentrations less than 1mM for all proteins studied. Moreover, it appears that the hydrophobic microdomain formed through polymerization of the terminal vinyl group of the monomer, SUS, is largely responsible for the superior binding capacity of poly-SUS. From these results, we conclude that the interactions of poly-SUS with the acidic proteins are predominantly hydrophobic and postulate that poly-SUS would produce superior interactions relative to SDS at low concentrations in polyacrylamide gel electrophoresis (PAGE). As predicted, use of poly-SUS allowed separation of the His-tagged tumor suppressor protein, p53, at sample buffer concentrations as low as 0.08% w/v (2.9mM), which is 24 times lower than required for SDS in the standard reducing PAGE protocol. This work highlights the use of poly-SUS as an effective surfactant in 1D biochemical analysis.

Comparison of poly(o‐anisidine) and poly(o‐anisidine‐co‐aniline) copolymer synthesized by chemical oxidative method

AbstractIn this study, poly(o‐anisidine) [POA], poly(o‐anisidine‐co‐aniline) [POA‐co‐A], and polyaniline [PANi] were chemically synthesized using a single polymerization process with aniline and o‐anisidine as the respective monomers. During the polymerization process, p‐toluene sulfonic acid monohydrate was used as a dopant while ammonium persulfate was used as an oxidant. N‐methyl‐pyrolidone (NMP) was used as a solvent. We observed that the ATR spectra of POA‐co‐A showed features similar to those of PANi and POA as well as additional ones. POA‐co‐A also achieved broader and more extended UV–vis absorption than POA but less than PANi. The chemical and electronic structure of the product of polymerization was studied using Attenuated Total Reflectance spectroscopy (ATR) and UV–visible spectroscopy (UV–vis). The transition temperature of the homopolymers and copolymers was studied using differential scanning calorimetry and the viscosity average molecular weight was studied by using dilute solution viscometry. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Comparison of poly- and monoclonal antibodies for determination of B-cell clonal excess in an routine clinical laboratory

Flow cytometry (FCM) has gained wide use in the determination of clonality in B-cell lymphoproliferative diseases and many methodological variations exist. We have compared the suitability of a) dual fluorochrome (FITC/PE)-labelled monoclonal antibodies, b) single fluorochrome (FITC)-labelled monoclonal antibodies and c) F(ab')2 fragments of FITC-labelled polyclonal antibodies for flow cytometric determination of clonality using commercially available software and a short sample preparation protocol. The FCM method was validated by analysis of immunoglobulin heavy chain and light chain gene rearrangements. We recommend the use of FITC-labelled monoclonals to obtain three parameters, the kappa/lambda ratio, D and D/S(n) values (Kolmogorov-Smirnov statistics) instead of the commonly used kappa/lambda ratio and D values only. This allows the use of a rapid sample preparation protocol to blood and bone marrow aspirates without sacrificing sensitivity or specificity obtained by the usual FCM method.

Phase Behavior of Polyelectrolyte Block Copolymers in Mixed Solvents

We have studied the phase behavior of the poly(n-butyl acrylate)-b-poly(acrylic acid) block copolymer in a mixture of two miscible solvents, water and tetrahydrofuran (THF). The techniques used to examine the different polymers, structures and phases formed in mixed solvents were static and dynamic light scattering, small-angle neutron scattering, nuclear magnetic resonance and fluorescence microscopy. By lowering the water/THF mixing ratio X, the sequence unimers, micron-sized droplets, polymeric micelles was observed. The transition between unimers and the micron-sized droplets occurred at X = 0.75, whereas the microstructuration into core-shell polymeric micelles was effective below X = 0.4. At intermediate mixing ratios, a coexistence between the micron-sized droplets and the polymeric micelles was observed. Combining the different aforementioned techniques, it was concluded that the droplet dispersion resulted from a solvent partitioning that was induced by the hydrophobic blocks. Comparison of poly(n-butyl acrylate) homopolymers and poly(n-butyl acrylate)-b-poly(acrylic acid) block copolymers suggested that the droplets were rich in THF and concentrated in copolymers and that they were stabilized by the hydrophilic poly(acrylic acid) moieties.

A Comparison of Poly(ether imide)s with 3-Phthalimide and 4-Phthalimide Units: Synthesis, Characterization, and Physical Properties

Bis(ether anhydride)s with 3- or 4-phthalimide moieties were prepared by reacting 3- or 4-nitrophthalodinitrile, respectively, with several diols and converting the resulting bis(ether dinitrile)s to bis(ether anhydride)s. Selected dianhydrides were converted into poly(ether imide)s in a two-stage solution polymerization and imidization process. It was found that, in most cases, the dianhydrides with 4-phthalic anhydride units gave high-molecular-weight polymers with any of several aromatic diamines. In contrast, dianhydrides with 3-phthalic anhydride units gave, primarily, low-molecular-weight products. Examination of several low-molecular-weight products by electrospray-ionization mass spectrometry demonstrated that the products consisted of small oligomers, cyclic or linear according to the structure of the diamine. A series of high-molecular-weight polymers were prepared from 4,4‘-bis(4‘ ‘-aminophenoxy)biphenyl (BAPB) and each of several bis(ether anhydride)s with 3- or 4-phthalic anhydride units; the anhydrides had isopropylidine or hexafluoroisopropylidine units or ortho-methyl or ortho-tert-butyl substituents in the diol residues. These polymers were characterized in terms of their molecular weights and glass-transition temperatures. The gas permeabilities, positron annihilation, and dielectric relaxation behaviors of the polymers were investigated and their properties related to their molecular structures. Dielectric relaxation spectroscopy measurements indicate that, in this group of polymers, the rates of the local chain mobility are comparable and are able to facilitate gas diffusion. An apparent linear correlation between the permeation coefficients and free volume as determined by positron annihilation lifetime spectroscopy was observed with certain gases. Comparison of polymers with similar molecular structures indicated that isomeric polymers with 3- and 4-linked phthalimide units have similar properties and that the introduction of branched chains or fluorinated groups leads to an increase in the free volume and consequently increased permeability.

Comparison of poly(ethylene oxide) crystal orientations and crystallization behaviors in nano-confined cylinders constructed by a poly(ethylene oxide)-b-polystyrene diblock copolymer and a blend of poly(ethylene oxide)-b-polystyrene and polystyrene

A poly(ethylene oxide)-b-polystyrene (PEO-b-PS) diblock copolymer with a number average molecular weight of PEO blocks, MnPEO=8.8kg/mol, and a number average molecular weight of PS blocks, MnPS=24.5kg/mol, (volume fraction of the PEO blocks, fPEO, was 0.26) exhibited a hexagonal cylinder (HC) phase structure. Small angle X-ray scattering results showed that the PEO cylinder diameter was 13.3nm, and the hexagonal lattice was a=25.1nm. The cylinder diameter of this HC phase structure was virtually the same as that in the blend system constructed by a PEO-b-PS diblock copolymer (MnPEO=8.7kg/mol and MnPS=9.2kg/mol) and a PS homo-polymer (MnPS=4.6kg/mol) in which the fPEO was 0.32. The cylinder diameter in this blend sample was 13.7nm and the hexagonal lattice was a=23.1nm. Comparing crystal orientation and crystallization behaviors of this PEO-b-PS copolymer with the blend, it was found that the crystal orientation change with respect to crystallization temperature was almost identical. This is attributed to the fact that in both cases the PEO block tethering densities and confinement sizes are very similar. This indicates that when the MnPS of PS homo-polymer is lower than the PS blocks, the PS homo-polymer is located inside of the PS matrix rather than at the interface between the PEO and PS in the HC phase structure. On the other hand, a substantial difference of crystallization behaviors was observed between these two samples. The PEO-b-PS copolymer exhibited much more retarded crystallization kinetics than that of the blend. Based on the small angle X-ray scattering results, it was found that in the blend sample, the HC phase structure was not as regularly ordered as that in the PEO-b-PS copolymer, and thus, the HC phase structure contained more defects in the blend. This led to a suggestion that the primary nucleation process in the confined crystallization is a defect-controlled process. The mean crystallite sizes were estimated by the Scherer equation, and the PEO crystal sizes are on the scale of the confined size.

A comparison of poly(ether imide)s from diamines with 2-aminophenoxy or 4-aminophenoxy units: Synthesis, characterization and properties

A series of new 3- and 4-ring bis(2-aminophenoxy) aromatic diamines were prepared. These, and corresponding, conventional bis(4-aminophenoxy) diamines were reacted with several aromatic bis(ether anhydride)s to form poly(ether imide)s. The diamines with 4-aminophenoxy groups gave high-molecular-weight polymers that were cast into films with good mechanical properties. In contrast, in almost all cases, diamines with 2-aminophenoxy groups only gave low-molecular-weight powdery products that could not be cast into coherent films. The low-molecular-weight products, prepared from stoichiometrically equal amounts of monomers, were examined by mass spectrometry and shown, in most cases, to consist primarily of cyclic oligomers; traces of linear oligomers were identified in some samples. Apart from a polyimide prepared from pyromellitic dianhydride and 4,4′-bis(2″-aminophenoxy)biphenyl, the only products found to contain significant proportions of linear oligomers were those prepared with a stoichiometric imbalance of monomers. End groups of the various linear oligomers were identified. The 2-aminophenoxy groups predispose the oligomers to cyclize as amic acids, and to remain as cyclics on imidization. In some cases [1+1] cyclic oligomers were observed although the most common species were the [2+2] cyclic dimers.