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Paper-based platforms for biological studies have received significant attention given that cellulose is ubiquitous, biocompatible, and can be readily organized into tunable fibrous structures. In the latter form, effect of complexity in surface morphologies (roughness, porosity and fiber organization) on cell-substrate interaction has not been thoroughly explored. We infer that altering the properties of a fibrous material should lead to significant changes in cellular microenvironment and direct the deposition of structurally analogous extracellular matrix (fiber-fiber templating) like collagen. Here, we elucidate the effect of varying paper roughness and surface chemistry on NIH/3T3 fibroblasts via organization of excreted collagen. Collagen intensity was found to increase linearly with paper porosity, indicating a 3D culture platform. The intensity, however, decays over time due to biodegradation of the substrate. Stability can be improved by introducing fluorinated alkyl silanes to yield hydrophobic paper. This process concomitantly transforms the substrate to a 2D-like scaffold where collagen is predominantly assembled on the surface, thus changing the cellular microenvironment. Altering surface energy also led to fluctuations in collagen intensity and organization over time for smooth (calendered) paper substrates. We infer that the increased roughness improves collagen adsorption through capillary driven petal effect. In general, the influence of the substrate simultaneously affects its ability to host collagen and guide orientation. These findings offer insights into the effects of secondary structures and chemistry of fibrous polymeric materials on cell culture, which we propose as vital parameters when using paper-based platforms.

We first summarize available experimental evidence indicating the existence of a second-order transition or relaxation region in atactic polystyrene at 60 to 100°C. above Tg. It increases from 137°C. at a molecular weight of 3000 to 192°C. at a molecular weight of 392,000. It appears in such diverse measurements as thermal expansion, heat capacity, x-ray studies, deformation-temperature plots, dynamic mechanical loss, stress relaxation, melt viscosity, and DTA. It may not appear if the test method is a very slow one, presumably because it merges with Tg. We ascribe this phenomenon to an ability of the entire polymer chain to act as a unit because of the available free volume and enhanced chain mobility at elevated temperatures. This is consistent with the fact that this transition shows up in melt viscosity studies and is completely suppressed by crosslinking. Since this represents a change from one liquid state to another, we designate this transition as Tl,l.

A selected group of standard atactic polymers with CC, CO, diene, and SiO backbones and some crystalline polymers for which an amorphous phase T g is known have T g 's which increase with the product of cohesive energy density (CED) times the characteristic ratio (C ∞), falling on either of two straight lines of positive slope, intersecting at T g =118 K. The principal difference between polymers on the two lines concerns their low-frequency mechanical relaxation spectra: upper line polymers tend to have a relatively strong T β ∼ 0.75T g , but weak or missing T γ

Introduction students in the biochemistry laboratory are introduced to the extraction and characterization of biomolecules, the tissue of choice is most often of animal origin. Plant products are seldom used; therefore, students rarely gain knowledge and appreciation of the unique biomolecules present in the plant kingdom. In order to fill in this gap, we have designed an experiment in which students isolate a mixture of pigments by solvent extraction of plant tissue, separate some of the components by chromatography and identify them by visible region spectrophotometry. Students who complete this experiment gain knowledge and technical skills in biomolecule extraction, chromatographic methods, spectrophotometric techniques and plant pigment structure. Students will follow procedures which are typical for the general extraction and characterization of lipids. However, unlike most lipids (especially those in animals), the plant pigments are highly colored and may be characterized and quantified by visible spectrophotometry. Theory Many of the colors associated with higher plants (green leaves in the spring and summer, yellow or red leaves in the fall, the orange color of carrots, some colors in flower petals) are due to the presence of pigment molecules. Review articles on plant pigments have been recently written by Goodwin 1 and Lichtenthaler. 2 General information on photosynthetic pigments can also be obtained from the standard biochemistry texts by Mathews and van Holde, 3 Stryer, 4 and Voet and Voet. 5 The major photosynthetic pigments of higher plants can be divided into two groups, the chlorophylls and the carotenoids. Both types of pigments are present in the subcellular organelles called chloroplasts, where they are bound to proteins in the thylakoids, the photochemically active photosynthetic biomembranes. Intact pigment-protein complexes, which are held together by weak, noncovalent bonds, have been isolated from chloroplasts and characterized b~( polyacrylamide gel electrophoresis and isoelectric focussing/The pigments are released in a protein-free form by grinding plant tissue in solvents such as acetone, methanol or hexane. Since the chlorophylls and the carotenoids are readily soluble in organic solvents, they are classified biochemically as lipids. The most abundant plant pigments are chlorophyll a and chlorophyll b which occur in a ratio (a:b) of approximately 3:1. As is shown in Fig 1, the chlorophylls possess a porphyrin ring with a coordinated magnesium atom at its center, a fused, 5membered ring and a C20 phytyl side chain. This nonpolar, HzC=CH H C~ "3~c#.

X-ray scattering patterns from amorphous polymers frequently contain halos corresponding to distances significantly greater than that of van der Waals packing of carbon atoms. Regularities in the positions of such halos as a function of pendant group size have been reported, primarily for the “crystallizable” comb polymers. This work concerns n-alkyl acrylate, n-alkyl methacrylate, and cycloalkyl methacrylate polymers with small alkyl groups: regularities in halo position with alkyl group size are seen, but the behavior with size is quantitatively different from that of the comb polymers. A case is made for the existence of a moderate amount of intersegmental order as the normal condition in the condensed amorphous state. The behavior of poly(methyl methacrylate) is anomalous and studies on it may not be used to generalize about the structure of the amorphous state.

Apoferritin catalyzes the oxidation of Fe(II) to Fe(III). Ferroxidase activity is assayed and characterized by coupling the oxidation with the binding of Fe(III) to transferrin. The initial rate of Fe(II) oxidation is dependent on apoferritin and initial Fe(II) concentration but independent of transferrin concentration. The ferroxidase activity is inhibited by Zn(II). Ferritins with varying loads of iron have the same ferroxidase activity level. It is suggested that the described oxidation process represents the initial step of iron deposition in apoferritin. Since transferrin can intercept Fe(III) before it is deposited in apoferritin, active sites for Fe(II) oxidation must be on or near the surface of apoferritin. This finding is contrary to the current view of apoferritin-catalyzed oxidation of Fe(II) which places active sites in the channels to the core or inside the central core.

Following a discussion of the historical perspective of the problem of order in amorphous polymers and a definition of terms, this paper reviews various topics in the literature. This problem and the related one of order in liquid alkanes (as a model for polyethylene) and amorphous polymers were omitted from or inadequately treated at this symposium. These topics relate both to short-range order (>50 A) and long-range order (>100 A) including supramolecular amorphous structure. Among the former are depolarized Rayleigh scattering and heats of mixing of normal alkanes; positron annihilation in polyisobutylene, x-ray scattering, dielectric loss data, and the constancy of the Tg/Tm ratio. Among the latter are the Mooney-Rivlin C2 constant and the general implications of short-range order for a supramolecular structure in long-chain polymer. Since local order exists in simple liquids, it must be present in amorphous polymers. A term, correlation of molecular orientations, CMO, introduced by Bothorel ...

The liquid state behavior of the following atactic polymers has been reviewed: the alkyl and cycloalkyl methacrylates; polyisobutylene; polybutadiene, its random copolymers with styrene and acrylonitrile, and S-B diblocks; polystyrene; and the poly-α-olefins C3, C5, and C6. Just as Tg manifests itself through time-dependent (relaxational) and thermodynamic (transition) effects, so also does a T Tg or Tβ relaxation. With increasing syndiotactic content, PMMA's reveal strengthening Tβ and Tl processes. Relaxation maps plotting log frequency-T−1 are presented for PBD and PIB, showing both Tg and Tl. The latter exhibits non-Arrhenius behavior with an activation enthalpy about half that at T...

The ESR spin-probe technique with the use of the nitroxide probe 2, 2, 6, 6-tetramethyl-4-hydroxypiperidin-1-oxyl benzoate (BzONO), has been used to study Tg variation in a series of polystyrenes of varying molecular weight and molecular weight distribution. Glass temperatures, as determined by ESR, for “monodisperse” polystyrenes vary smoothly as a function of molecular weight. From results on polystyrene binary blends it is shown that the technique is responsive to M n rather than M w. Data obtained by ESR are shown to agree with conventional DSC measurements. Some advantages, limitations, and implications of the technique are also presented and discussed. The actual shapes of extrema separation vs. temperature plots are functions of molecular weight (becoming broader as molecular weight increases) and are discussed in terms of free volume effects.

Ten areas of the field, all with some special interest to the author, were selected for predictions about the near future. In order to gain perspective, a brief review is presented of some key developments which occurred after the publication of the book ‘Anelastic, and Dielectric Effects in Polymeric Solids’ by McCrum, Read and Williams in 1967. The following predictive areas are then discussed in varying degrees of detail. (1) Apparatus: current status and the need for automation and more sophistication. (2) Extending the temperature range above T g or T M and the molecular weight range down to the oligomers. (3) Study of rarefied polymers (higher than normal free volume). (4) Nature of the in-chain β relaxation ( T T g ) in addition polymers. (5) Use of nitroxide probes as an auxiliary tool to study amorphous phase relaxations in highly crystalline polymers. (6) Computer simulation of molecular motion at sub-group relaxations. (7) Nature of the amorphous state and its possible effect on mechanical relaxations other than through free volume. (8) Correlation between mechanical strength of glassy polymers and secondary, glassy state relaxations. (9) The need to prepare highly crystalline polymers in the completely amorphous state. (10) The impact of new polymer types. It is concluded that mechanical spectroscopy is still a quite viable field with exciting potentialities. A synergism between automation of apparatus, new materials, new techniques (not necessarily in the field of mechanical spectroscopy) and theory is anticipated.

Bean plants (Phaseolus vulgaris L.) were cultured in nutrient solutions containing three concentrations of iron. The leaves of plants grown with a limiting supply of iron contained reduced levels of protein, chlorophyll and the iron‐containing enzyme, lipoxygenase (EC 1.13.11.12). Measurements of lipoxygenase made on leaf crude extracts did not correlate with iron supply; however, upon purification of the enzyme by affinity chromatography, a direct correlation was observed. The lack of correlation was partly due to the presence of chlorophyll, an inhibitor of lipoxygenase, in the crude extract. Lipoxygenase levels changed with age of the plants, but rose to a maximum at days 14–16. A comparison of leaf lipoxygenases grown with different iron supply showed that they were identical with the same pH profile, chlorophyll inhibition, reaction products, and electrophoretic mobility. It is suggested that lipoxygenase may be used as a probe to evaluate iron availability and to investigate iron metabolism...

We start with two previously calculated semi-empirical equations: (1) C 2 C 1 = K 1 A −2 (for 2 C 1 = 0.2 MPa). K 1 is a constant and A is the area per polymer chain; (2) N c = K 2 A 0.67 where K 2 is another constant. It follows from these two relationships that: C 2 C 1 (at 2 C 1 = 0.2) = K 3 N −3 c . N c , determined for bulk polymers, increases on dilution with a solvent according to N c ( o 2 ) = N c ( o 2 = 1) o − r 2 where o 2 is the volume fraction of elastomer and r is a constant for a given elastomer, usually unity. For vulcanizates prepared in the presence of diluents but tested in the bulk state, one predicts C 2 C 1 = K 4 o 3r 2 if entanglements are the sole source of the C 2 term. Plots of log C 2 C 1 against log o 2 show slopes ranging from 0.5 to 3.0 but more commonly near unity. There is wide discrepancy between different authors. We conclude that chain entanglement cannot be the sole source of the C 2 term but that several factors probably operate. Different theories and ideas about the origin of the C 2 term are briefly reviewed. Excellent linear plots of log C 2 C 1 against log 2 C 1 are presented for trans -polypentenamer and for Hevea rubber. In general, sufficient data for the rigorous testing of the C 2 C 1 —o 3r 2 relationship are not available. A correlation of f e f with area per chain (where f e is the energetic contribution to the total force, f ) increases rapidly at small areas but levels off above ∼ 0.4 nm 2 . All studies reported herein are based on published data.

Torsional braid analysis (TBA) (∼0.3 Hz) and differential thermal analysis (DTA) data are presented for the temperature for the region 0–200°C for two series of atactic polystyrenes with narrow molecular weight distributions: (a) anionic series, Mn = 600–2×106, Mw/Mn ≃ 1.1; (b) fractionated thermal series, Mn = 2,000–1.1×105, Mw/Mn Tg and (b) that Tll reflects chain entanglements, further suggest that Tll involves a longer chain segment length and possibly the entire molecule. Comparison of Tll versus log M plots with T versus log M isoviscous state plots based on zero-shear melt viscosity data from the literature implies that Tll measured by the TBA technique corresponds to an isoviscous state of 104–105 poises. The employment of narrow molecular weight polymers is presumably responsible for both the linear variation of the Tll transition with Mn−1 (which suggests a free volume basis for the relaxation) and the form of the variation of the Tll transition with log M (which suggests an isoviscous basis for the relaxation). The sharpness of the Tll loss peak by TBA decreases with increasing molecular weight and dispersity. The DTA endothermic event corresponding to Tll is clearly related to the occurrence of flow since the fused films which result from heating granules to 200°C and cooling to R.T. do not reveal a Tll on reheating. If a fused film is crushed, a Tll event is observed on heating. For bimodal blends with Mn < Mc for both components, the Tll transition was averaged; with one component less than and one greater than Mc, the Tll transitions of the components appeared to occur independently at temperatures corresponding to those of the isolated components. In accordance with Ueberreiter and Orthmann, Tg appears to separate a glassy state from a fixed liquid state, whereas Tll separates the fixed liquid from a true liquid state. Possible molecular interpretations for the Tll process are discussed. Systematic bodies of data from the literature which indicate the presence of the Tll process in other polymers are summarized.

Dynamic dielectric studies of oligomeric poly(propylene oxide) (PPO) of M n =3034 , between −10° and 40°C at 0.1, 1, and 10 KHz, reveal a glass transition and a T >Tg liquid-liquid transition. Analysis of d ϵ′ d T in the liquid region of PPO also indicates the presence of T11. The activation enthalpies for the Tg and T11 transitions have been calculated to be 39 and 18 kCal mol−1, respectively. The T11 transition in poly(propylene oxide) has been assigned to the motion of the entire polymer molecule.

This report summarizes some initial results on the use of a perforated brass shim stock support to extend the useful range of dynamic mechanical testing well over 100 degrees above the traditional limiting polymer softening points of Tg or Tm. Weak secondary relaxations were observed above Tg in both polyisobutylene (PIB) and polystyrene (PS) homopolymer, copolymer, and blend systems and above Tm in gutta percha (trans-polyisoprene). The DuPont 981 Dynamic Mechanical Analyzer (DMA)–990 Thermal Analyzer system was used to characterize these weak liquid state processes. The DMA instrument deforms the specimen in flexure, thus minimizing the shear component present in some other techniques. Specimen-coating weights are typically in the range 20–40 mg. The perforations are particularly useful for polymers having low inherent adhesion to metals or systems which are very brittle in the glassy state, e.g., low MW PS's and many methacrylates.

It is known that the x-ray scattering pattern of an amorphous polymer may contain one or more halos corresponding to van der Waals spacings or larger. In this work we found that (i) the halo positions (and equivalent Bragg spacings) vary systematically with the cross-sectional area of the polymer chain in the crystal and (ii) there are at least two families of such halos with spacings larger than that of van der Waals contacts of atoms. From the wide variety and nature of the polymers considered, this behavior is believed to be representative of the amorphous state existing in polymeric samples. This work indicates that there is a degree of packing regularity in amorphous polymers that should be considered in models and theories of polymer chain conformation.

Reexamination of published DSC traces for first and second heatings of atactic polystyrenes with Mn from 2050 to 1.99 × 106, Mw/Mn ∼ 1.1, is discussed in terms of some newly enunciated principles of calorimetry for the liquid state of atactic polymers. These traces were originally stated to reveal only an endothermic peak above Tg, identified with Tll at Mn Tll is indicated.

The thermally stimulated current (TSC) technique has been used to investigate three anionic polystyrenes of Mn 17,000, 71,700, and 1.55 × 106, i.e., M Mc, and M ≫ Mc, where Mc is the entanglement molecular weight. A current maximum near Tg designated TMg, has relaxation times which follow an Arrhenius equation. A second current maximum at T > Tg appears to be the Tll process and is designated TMll. Relaxation times for it follow a Vogel equation. TMg and TMll vary with molecular weight, increasing below Mc and leveling off above Mc at a temperature of about 170°C. Values of TMg and TMll are compared with values of Tg and Tll obtained from torsional braid analysis, which involves melt flow; and with differential-scanning-calorimetric values on fused films, where there is no transport of polymer. It is concluded from such cross-comparisons that TSC, at least for polystyrene, is a quasistatic test which may involve microscopic viscosity. Macroscopic viscosity does not play a role. The ratio TMll/TMg is in the range 1.10–1.16, similar to Tll/Tg values by other methods. A few comments about Tll in atactic poly(methyl methacrylate) by the TSC method are given.

Considerable confusion exists in the literature concerning the glass temperature, Tg, of many highly crystalline polymers, in particular, linear polyethylene (PE), poly(vinyl fluoride) (PVF), poly(vinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), poly(oxymethylene) (POM), and poly(ethylene oxide) (PEO). We attempt to resolve some of this confusion first, by defining the nature of the problem; second, by developing criteria for defining the locations along a relative temperature scale (T/Tg or T/TM) of the key relaxations and transitions, Tg, T < Tg, TM, and Tαc for C-C and CO backbone polymers free from long alkyl side groups; third, by developing a set of typical mechanical relaxation spectra for amorphous, semicrystalline, and single crystal materials of known Tg; fourth, by defining the concept of a double glass transition with values Tg(L) and Tg(U) and the optimum conditions for observing same. Finally, we apply these concepts and criteria to resolving the value of Tg for PVF and PVDF. Criteria employed include ratios of relaxation temperatures such as (T < Tg)/Tg, Tαc/TM, and Tg/TM, typical activation enthalpies for various relaxation processes, thermal expansion and heat capacity data. Two theoretical subjects are explored: the effect of crystallinity on increasing Tg and the effect of crystallinity on the relative strengths of the Tg and T < Tg processes. We also employ a “comparative anatomy” technique of comparing temperatures and related activation enthalpies of the several relaxations and transitions for a series of closely related polymers such as PE, PVF, PVDF, PTFE, Polytrifluorochloroethylene, and poly(vinyl chloride). We suggest that a new scientific discipline of interpreting the relaxation spectra of crystalline polymers may be emerging through integration of a large body of literature, the refinement of old criteria, and the development of new criteria. Even so, we are not yet able to offer a satisfactory interpretation of the relaxation spectra for POM and PEO.

We first summarize in a table the salient features of three dynamic mechanical measuring instruments featured at this symposium: torsion pendulum, torsional braid and Rheovibron viscoelastometer. It is concluded that while each instrument performs one or more functions better than the other, there is a tendency for all three instruments to approach each other's capabilities with time. Some general observations are presented about the main uses of dynamic mechanical testing and about the nature of mechanical loss spectra. The correlation of these mechanical loss spectra with other types of physical measurements is stressed. The Simha-Boyer free volume quantity, Δα Tg, is shown to decrease with trans content in a series of butadiene polymers and copolymers, presumably because of an in-chain crankshaft loss mechanism whish generates free volume in the glassy state. Related cases for the nylons, ethylene-vinylacetate copolymers, and polyethylene are cited. It is suggested that the strength of T < tg ...

Using objective computerized statistical procedures, we have examined high precisionC p data by DSC reported by Wunderlich and Gaur for a series of alkyl acrylate and methacrylate polymers. Although they claimed the data to be linear inT aboveT g , our results do not support the linear model. One or two endothermic slope changes are revealed aboveT g in lowT f polymers (T f < 20 °C) and at least one exothermic slope change in highT f polymers (T f > 20 °C).T f is the flow temperature of Ueberreiter. Both the first endotherm and the first exotherm occur near (1.22 ± 0.07)T g , suggesting aT ll type phenomenon.T ll varies as $$1/\bar M_n $$ . The first exotherm is associated by us with wetting of the DSC pan by molten polymer on the first heating of particulate highT f polymers. The rate of wetting, and presumably the magnitude of the exotherm, depends in part on the ratio,γ/η, whereγ is surface tension andη is melt viscosity of the molten polymer. Sinceγ is relatively constant, the molecular weight and temperature dependence for rate of wetting resides inη, which depends on $$\bar M_w $$ . For $$\bar M_n > > \bar M_c $$ , a second exothermic event caused by sintering, and also controlled by η, may be present. The interactive roles of $$\bar M_n ,\bar M_w ,\bar M_w /\bar M_n $$ ;M c (entanglement molecular weight); particle size, and heating rate onC p —T behaviour are delineated for the first time. LowT f hydrocarbon polymers, namely atactic polyalphaolefins,C 3 ,C 5 ,C 6 ; PIB; and dienes, PBD and cis-PI, exhibit single or double endotherms. Other results on highT f polymers showing exothermic effects, notably PS, PnBMA and polyglycidylmethacrylate are cited.

Polymers under discussion can be represented by [CH2)nR]p where R is CH2, CF2, O, S or CH = CH; and where n can vary from 0 to ∞. The copolymer, P(ethylene-alt-TFE) is also included. These polymers tend to be highly crystalline with resultant confusion about their Tg and hence their Tg/Tm values and a clarification scheme is proposed in which it is considered that each such polymer has a double glass transition, Tg(L)/f(χc), Tg(U) = F(χc); and a sub-glass T

We started with a critical examination of published Mooney-Rivlin constants on the common commercial elastomers and some experimental ones. Following a suggestion by Treloar, plots were made of C2/C1 against 2C1 in order to select values of the ratio at constant 2C1 in comparing all elastomers. We found empirically that a log-log plot of C2/C1 against 2C1 seemed to be either linear or slightly concave downwards. This fact facilitated the extrapolation which was necessary in several instances. Cross-sectional areas of elastomer chains in the amorphous state were assumed to be proportional to areas for the same polymers in the crystalline state. (The areas of copolymers were obtained from an averaging process of the areas of the corresponding crystalline homopolymers.) A plot of log C2/C1 against log (area per chain) is linear, as seen in Figure 7, with a slope of about −2. This is, to our knowledge, the first positive correlation of Mooney-Rivlin constants with a specific molecular parameter. It is also one of the first uses of tabulated lattice parameters in structural correlations. Vincent had previously correlated tensile strength of polymers with cross sectional areas per chain. Speculations are presented concerning the implications of the linear relationship in Figure 7. They are divided as between stress-induced local ordering favored by some authors and chain entanglement favored by others. A third possible effect active in readily crystallizable elastomers is strain-induced crystallinity. This paper does not attempt to resolve the conflict between these several alternatives. One by-product of this study is the fact, shown in Figure 9, that C2 at constant C1 increases linearly with molecular weight for cis-trans-vinyl poly-butadienes at low 2C1 but not at high 2C1. This might be consistent with an entanglement mechanism. There is, however, a more important byproduct. Regardless of the molecular interpretation of Figure 7, such a correlation provides a convenient criterion for judging the validity of divergent sets of literature data. Specific examples of this will be discussed in Appendixes 2 to 4. Gaps and scatter in literature data became quite apparent as with butyl rubber and PDMS. Finally, we note the predictive features of Figure 7 in suggesting experiments to carry out on elastomers chosen on the basis of cross-sectional area. Thus, poly(di-n-propylsiloxane) might be expected to show a vanishingly small C2 at any practical level of crosslinking even though, from Vincent's correlation, its strength might also approach zero. In particular, the lower left hand corner of Figure 1 lends itself to such exploration. We obviously could have predicted7 the C2/C1 values later reported by Mark et al. for poly (ethyl acrylate). We have examined most of the available Mooney-Rivlin C1 and C2 values by an objective technique. As a consequence, we are able to pinpoint some unresolved problems which might otherwise not be obvious: many gaps exist in the literature data (for example, it is not possible to prepare a Figure 1 type plot for butyl rubber); many discrepancies remain to be clarified; and key characterization parameters are absent for many elastomers.

The accomplishments of Borden Award Winner John K. Gillham and his colleagues using Torsional Braid Analysis (TBA) and Differential Scanning Calorimetry (DSC) to investigate the Tg and T > Tg or Tu regions of anionic and thermal poly styrenes (PS) are evaluated and related to work on PS and other polymers and to controversies surrounding TBA and the Tu transition. Arguments are presented to refute the contention that Tu by TBA is an artifact produced by the braid and the contention that Tu has a relaxational nature but no thermodynamic basis. Two distinct behavior patterns are found for Tu vs log Mn plots: quasi-static methods such as DSC on fused films show Tu to level off above Mc and approach an asymptotic value of ∼435K; dynamic methods involving melt flow show that Tu increases without limit above Mc because of entanglements. A compilation is presented of 25 investigations of Tu on polybutadiene, poly(methyl methacrylate) (PMMA), PS, plasticized PS, and atactic polypropylene, involving twenty experimental techniques. The behavior of zero shear melt viscosity for PS is summarized. Gillham's work has not only led to clarification of many isolated papers in the literature but has also inspired various parallel experimental and literature studies on Tu. We conclude that Tu is a molecular level transition which, like Tg, exhibits both kinetic (relaxational) and thermodynamic aspects. It is shown that heat capacity should be a more sensitive method than dilatometry for studying the Tu transition.

It is shown that the 13C NMR spectral collapse temperatures Tc reported by Axelson and Mandelkern tend to give a constant ratio of Tc/Tg averaging 1.21 ± 0.05 and independent of Tg or of polymer structure. It is further shown that Tc is not a high-frequency value for Tg because this would require Tc/Tg to decline with increasing Tg. Tc/Tg agrees in numerical value with Tu/Tg, where Tll is the liquid-liquid transition lying above Tg. Direct comparison of Tc and Tu for four polymers PIB, PnBA, atactic PP, and isotactic PMMA shows very close agreement. The various results suggest, but do not prove, that Tc from 13C NMR spectroscopy may be a new, direct measure for Tll. A measured Tc of 233K for linear PE is compatible with a Tg near 195 K (233/195 = 1.19), whereas a Tg of 148 K gives the ratio 233/148 = 1.57, which is outside any value shown in tabulated form.

ESR spin-probe values of glass temperatures are reported for a series of di-, tri-, and radial block copolymers. With one exception, in which the hard phase is poly(t-butylstyrene), the hard component is polystyrene (PS); the soft components include polybutadiene (PBD), polyisoprene (PI), hydrogenated PBD, hydrogenated PI, and poly(dimethyl siloxane) (PDMS). Tg's of the soft phase are in general agreement with those of the respective high molecular weight homopolymers; Tg's of the hard phase generally deviate widely from those of corresponding high molecular weight homopolymers. This deviation is interpreted in teens of a number of factors, including, the molecular weight of the hard phase, differences in solubility parameters for the two phases, percent of the hard phase present, and the presence of crystallinity. Comparison of Tg's determined by ESR with Tg's from dynamic mechanical methods on S-B-S triblocks of similar composition demonstrates that the ESR method is measuring the Tg of the interpliase and hence, in principle, its composition.

The quantity ΩCpTg for 30 different polymers averages 27.5 cal g−1 but is given more accurately by ΩCpTg = 15 + 4 × 10−2 Tg. There is a good linear correlation between ΩCp and the difference, Ωβ, in thermal expansion, dV/dT, above and below Tg. This correlation can be explained empirically since both ΩCp and Ωβ are inversely proportional to Tg. It can also be explained by the fact that Tg is directly proportional to the energy of hole formation eh. We show that the coefficient of expansion in the liquid state a t varies inversely with eh. We finally note the similarity of hole volumes vh as calculated from hole theory and the free volume quantity ΩαTg from Simha and Boyer. The various intercomparisons given in this paper between specific heat and thermal expansion quantities allow one to assess conflicting literature data in either of these disciplines.

This paper attempts to interrelate three important aspects of plasticizer behavior: compatibility or how much plasticizer can be added without causing phase separation; efficiency, or how much a given amount of plasticizer lowers the brittle temperature; and permanence, or how well a plasticizer is retained by the polymer on heat aging or solvent treatment.Compatibility is discussed in terms of the Flory‐Huggins theory of the thermodynamics of polymer solutions, which relates the activity of the plasticizer to its concentration in the polymer. Efficiency is measured by how the plasticizer lowers the melt viscosity of the polymer. An empirical relationship between efficiency and μ (the Huggins polymer‐solvent interaction constant) is shown. Loss of plasticizer at elevated temperatures depends in part on the effective vapor pressure of the plasticizer, and in part on how rapidly diffusion of plasticizer from the interior of the sample replenishes that lost from the surface. From the fact that diffusion cons...

Considerable progress has been made in the past 20 years in the synthesis, characterization and fabrication of plastics. Previous SPE Award winners, such as Mark, Natta, and Marvel dealt largely with synthesis; Flory with characterization; Alfrey and Du Bois with fabrication. One of the still unsolved problems lies in the realm of relating mechanical properties, such as impact strenght and creep to molecular structure. The design enginner who wishes to use a plastic part is concerned primarily with how some property such as impact strenght varies with temperature, speed of test, test method, etc. The polymer scientist must know why. Through knowing why, he may be able to design better plastics. This paper attempts to survey some of the world-wide progress made in this area in the past 10 years. The ultimate goal is to understand these mechanical properties in terms of internal molecular motions which occur in solid polymers. Internal motion can be detected by electrical, electromagnetic and dynamic mechanical measurements. When these three methods are applied on a given polymer over a range of temperatures, insights can be gained as to the variation of impact strength and other properties with temperature and frequency for that same polymer. These three fundamental methods, which require very small samples (less than 50 grams), can provide insight into the practical behavior of plastic materials over the wide range of temperatures and frequencies encountered in the real world.

The density-gradient tube is a special glass vessel in which a vertical linear density gradient of almost any desired magnitude can be maintained in a stable condition for prolonged periods by using liquids or solutions of the proper density. This article describes the application of such a device to three typical problems appearing in the field of high polymers: crystallization-rate data, inhomogeneities in composition of copolymers, and rates of polymerization. Possible application to still other problems is indicated.

Details of our synthesis of 5-aminomethyl-4,3′-dicarboxymethyl-3,4′-di-(2-carboxyethyl)-dipyrrylmethane (1b), as a stable potassium salt are now reported. This synthetic product had been shown to be an intermediate in the biosynthesis of uroporphinogen 1. The analogous tripyrrane, 15, should be available from the lactam of 2-(2-methoxycarbonylethyl)-3-methoxycarbonylmethyl-4,6-di-(2-ethoxycarbonylethyl)-5-ethoxy-carbonylmethyl-7-carboxymethyl-8-aminomethyl-tripyrrane (22) which has also been synthesized.5-Formyl-4,3′-di-ethoxycarbonylmethyl-3,4′-di-(2-ethoxycarbonylethyl)-5′-benzyloxycarbonyldipyrryl-methane (24), was obtained through the condensation of the bromomethyl pyrrole 2b with the hydrazone, 23, from a 2-formyl-5-free pyrrole and Girard's "T" reagent. This depends on the supression of the deactivating effect of the aldehyde group in a hydrazone from which the aldehyde is easily regenerated.

When a cross‐linked polymer initially swelled to its equilibrium volume in pure solvent is transferred to a solution of a high polymer in the same solvent and at the same temperature, the gel deswells. A quantitative treatment of this effect is given in terms of the Flory‐Rehner theory of the thermodynamic properties of gels, and the Flory‐Huggins theory of thermodynamics of high polymer solutions. The extent of deswelling depends on the molecular weight and concentration of the solute, on the solvent‐polymer interactions, and on the degree of cross‐linking in the gel. It thus offers in principle a new method for determination of the number average molecular weight of the solute. Various calculations are presented to show the extent of deswelling under given conditions. Finally, some experimental data is offered to demonstrate determinations of molecular weights, using styrene‐divinyl‐benzene copolymer gels and polystyrene solutions.

This paper concerns an empirical linear relationship between the melting temperature T1 and the second‐order or glassy transition temperature T2 for partially crystalline polymers. Two lines can be drawn, one for symmetrical polymers, the other for unsymmetrical polymers, the latter being of lower slope. These families are only approximate. It is shown for a limited group of polymers, that T2 is proportional to the cohesive energy density of the polymer. Since T1=ΔH/ΔS, it is suggested that the two families of curves arise because of differences in ΔS which depends on symmetry and chain stiffness. It is shown that T1 and T2 are linearly related with diluent as a common parameter.

The primary purpose of this paper is to summarize some of the general relationships between chemical structure and transition temperatures for polymers. In addition to the two primary transitions, the melting point Tm, and the glass transition TG, other transitions occurring either below TG or between TG and Tm are discussed. A secondary purpose of this paper is to make a preliminary attempt at some rational nomenclature and classification scheme for polymer transitions, especially in the case of polymers having multiple transitions. This article is not intended to be a complete review of the literature on transitions in polymers. Our paper was inspired by a comprehensive lecture on multiple transitions presented by Dr. Karl Wolf in Midland, Michigan, during the summer of 1960. The substance of this lecture has recently been published. Willbourn has also been concerned with the classification of multiple transitions. A recent comprehensive report by Saito, Okano, Iwayanagi and Hideshima called “Molecular Motion in Solid State Polymers” also considers in elaborate detail many of these same problems.

Since both the second‐order transition temperature and the tensile strength of plasticized polymers decrease linearly with plasticizer content, and frequently in inverse proportion to the molecular weight of the plasticizer, it was predicted that a linear relationship should exist between tensile strength and transition temperature for plasticized polymers, independent of the nature of the plasticizer. Tensile strength versus heat distortion for four different plasticizers in polystyrene follows this prediction very well. However, tensile strength versus brittle temperature for plasticized Vinylite VYNW gives a different straight line for each plasticizer. It is suggested that the diffusion rate of a plasticizer molecule is important in the fast brittle point test. The hypothesis is proposed that the brittle temperature of a plasticized polymer represents an isodiffusion constant state. It follows on the basis of some semi‐empirical equations that the brittle temperature should decrease linearly with plasticizer content, and inversely as the activation energy for diffusion of the plasticizer molecule in the plasticized polymer. This latter prediction appears in accord with existing data. This diffusion concept allows one to predict that the brittle temperature should increase linearly with logarithm of frequency of the test, but inversely as the activation energy for diffusion.

The nature of the thermal expansion anomaly in high polymers, known as the second‐order transition, is examined in some detail. It is suggested that below the transition temperature, Tm, polymer chains can expand sidewards but not parallel to their length. At Tm lengthwise expansion becomes prominent, thus accounting for the sudden increase in thermal expansion. Experimental results are presented showing the anisotropic expansion of oriented polymers below Tm. The transition effect is then treated as a problem in viscous flow, which gives rise to various semi‐empirical plots connecting Tm with applied forces, plasticizer content, and time effects. The brittle point, Tb, involves highly elastic deformation, and is shown to be a fundamentally different test, although Tm and Tb are sometimes numerically equal. Various factors influencing the brittle point are reviewed briefly.

This paper is concerned with the description of a simple technique for determining the molecular weight distribution curve of polystyrene (and presumably any other soluble polymer consisting of a polymer-homologous series). The general theory of the method as well as preliminary experimental results will be covered. The method is characterized by: (1) simple technique and equipment; (2) no need to isolate and measure fractions; and (3) a general basis in thermodynamic theory of polymer solutions, although a double calibration is needed to determine numerical parameters. The method consists in adding increasing quantities of nonsolvent to a dilute solution of polystyrene in a good solvent and observing the cumulative volume of precipitate as a function of nonsolvent content. The settled gel must re-equilibrate (hence deswell) with the new solvent after each alcohol addition. The swelling ratio, S (cc. of swollen gel per gram of dry polymer), of the swollen precipitate is approximately independent of the molecular weight and depends mainly on the volume percent of nonsolvent, γ according to ((1)) where α, σ, and s are constants. Likewise, the molecular weight, M, of the species precipitated at any nonsolvent content is given by the Schulz precipitability equation: ((2)) where α, β, and m are constants. For the system polystyrene–benzene–methanol, we find s = 4/3 while Schulz had already noted that m = 2/3. Elimination of γ and α leads to the prediction of a linear relation between M and S2. A two-fold calibration to obtain the constants in equations (1) and (2) is necessary to convert the observed data to an absolute cumulative weight versus molecular weight curve. However, even the simple plot of cc. of precipitate versus percent nonsolvent is informative. The relationship of these results to the thermodynamic theories of polymer solutions of Flory, Huggins, Gee, and Scott is outlined. The plot of cumulative volume of precipitate against percent nonsolvent has two characteristic features: an inflection point and a maximum. If the original polymer has a weight distribution function of the Schulz type, i.e., MkM × (1 − k)2, where k is related to the number-average molecular weight, Mn, through Mn = M0(1 − k)−1, then it can be shown that the maximum occurs at Mn while the inflection point occurs at 2.15 Mn.

Some preliminary results are reported on measurements of molecular weight distributions for polychlorostyrene. The following technique of isolating single polymer molecules is used: A precipitating agent, such as propanol, is added to a very dilute (1 ppm) solution of the polymer in benzene, presumably causing the molecules to coil up. Drops of this mixture are evaporated on a silica screen and examined in the microscope. Circular particles ranging in diameter from 15A to 500A and believed to represent single polymer molecules have been obtained on various polymers. The relationship between measured particle diameter and molecular weight is reviewed in some detail. The data appear to favor the concept of a random coil to the extent that particle diameter varies as the square root of the molecular weight. The molecular weight distribution curves obtained are of the expected shape and extent, although the average molecular weights computed from the distribution curves are 4–5 times greater than values measured by an independent method. Finally, the role of electrical charges in stabilizing isolated polymer molecules is discussed.

The results presented here on second-order transitions are in general accord with what has been known for other high polymeric systems. The value of the volume-temperature technique for investigating the nature of polymeric mixtures and the homogeneity of copolymers has been emphasized. In Part II a theoretical treatment of second-order transition effects, including the related brittle point determination, will be given. Finally, Part III will permit a more expanded treatment of the behavior of Saran and other crystalline polymers.

The ratio of tensile strength of a polymer at 25°C. to its melt viscosity at some elevated temperature in the fabrication range is suggested as a quantitative figure of merit for commercial polymers. This ratio goes through a very sharp maximum as a function of molecular weight. The height of the maximum drops sharply with increasing molecular weight heterogeneity, although the location of the maximum along the molecular weight scale is unchanged. This behavior follows because tensile strength depends on number-average, and melt viscosity on weight-average, molecular weight. The possible role of non-Newtonian behavior on these conclusions is discussed. Finally it is shown that the ratio of tensile strength to melt viscosity for a plasticized polymer increases exponentially with plasticizer content.

The phase separation in solutions of high polymers in the same solvent (technically known as incompatibility) has been studied for fourteen high polymers (cellulose, vinyl, and acrylic derivatives) dissolved in thirteen solvents. The influence of solvent, concentration, molecular weight and constitution of the macromolecules has been studied for 78 mixtures: the results are represented in triangular diagrams. Incompatibility appears to be the normal situation, compatibility the exception. Moreover, in cetain cases the exception may be only apparent. Phase separation is discussed in its relation to osmotic pressure, solubility, and the isomorphism of the molecules. Phase separation furnishes new means—useful at leat for technical research—of measuring the molecular weight of macromolecules. It is a simple and rapid procedure.