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PubMed1995

Drug release from hydrophilic matrices. 2. A mathematical model based on the polymer disentanglement concentration and the diffusion layer.

A comprehensive model is developed to describe the swelling/dissolution behaviors and drug release from hydrophilic matrices. The major thrust of this model is to employ an important physical property of the polymer, the polymer disentanglement concentration, rho p,dis, the polymer concentration below which polymer chains detach off the gelled matrix. For (hydroxypropyl)methylcellulose (HPMC) in water, we estimate that rho p,dis scales with HPMC molecular weight, M, as rho p,dis varies M-0.8. Further, matrix dissolution is considered similar to the dissolution of an object immersed in a fluid. As a result, a diffusion layer separating the matrix from the bulk solution is incorporated into the transport regime. An anisotropic expansion model is also introduced to account for the anisotropic expansion of the matrix where surface area in the radial direction dominates over the axial surface area. The model predicts that the overall tablet size and the characteristic swelling time correlate with rho p,dis qualitatively. Two scaling laws are established for fractional polymer (mp(t)/mp(infinity)) and drug (md(t)/md(infinity)) released as mp(t)/mp(infinity) varies M-1.05 and md(t)/md(infinity) varies M-0.24, consistent with the limiting polymer molecular weight effect on drug release. Model predictions for polymer and drug release agree well with observations, within 15% error. Evolution of water concentration profiles and the detailed structure of a swollen matrix are discussed.

Benzodiazepines↗

PubMed1999

Effects of Secondary Polymer Covalently Attached to Monodisperse, Poly(maleic anhydride-styrene)-Modified Colloidal Silica on Dispersibility in Organic Solvent.

Effects of surface-grafted polymer on the dispersibility of polymer-silica composite particles in ethyl acetate-methanol cosolvent were investigated. The composite particles were prepared by a two-step modification of monodisperse colloidal silica (120 nm in diameter). Modifications were carried out by first reacting the surface silanol of the colloidal silica with maleic anhydride-styrene copolymer silane coupling agent to prevent aggregation and then grafting, in acetone or tetrahydrofuran, amino group-terminated poly(methyl acrylate), poly(methyl methacrylate), or polystyrene to the maleic anhydride moiety on the surface. For poly(methyl acrylate) and poly(methyl methacrylate) graftings, composite particles with long polymer chains aggregated in methanol-rich cosolvent due to insoluble secondary polymer chain interaction among the particles. Particles with a small amount of relatively low-molecular-weight secondary polymer were dispersible in the methanol content range from 0 to 90 vol%. Polystyrene-modified particles never aggregated, even in 90 vol% methanol solution. An ESR study of the suspension in ethyl acetate-hexane cosolvent suggested that the dispersibility of these composite particles in ethyl acetate-rich solution is attributable to steric repulsion between solvated and expanded secondary polymer chains among the particles. The dispersibility of the composite particles in methanol-rich solution was controlled by a delicate balance between the electrostatic repulsion and the interparticle attraction due to the desolvated and insoluble polymer chain interaction among the particles. Copyright 1999 Academic Press.

Journal Article↗

PubMed2000

Fourier-Transform Infrared Spectroscopy Studies of the Interaction of Functionalized Siloxane Polymers with Porous Silica.

Adsorption behavior of the siloxane polymer, cyanopropylmethyl-phenyl-methyl-siloxane, in contact with a mesoporous silica has been investigated by Fourier-transform infrared spectroscopy (FT-IR) using a series of physically modified materials with different coating levels up to 20 w/w%. The nitrile stretch bands, which are observed in the 2150-2350 cm(1) range, exhibited complex profiles due to a variety of interactions of the cyano groups within the polymer and with the surface silanols. These complex bands have been resolved into multiple components using a curve-fitting procedure. Three major spectral components have been found and assigned to the nitrile stretch in the bulk polymer, interfacial polymer, and polymer attached to surface silanols via hydrogen bonding. The latter spectral component is dominating for the samples with low coating levels. Its relative contribution decreased with the increasing amount of the polymer on the silica surface due to increasing contribution of the pure-polymer spectral component. Copyright 2000 Academic Press.

Journal Article↗

PubMed1978

Immune responses of inbred guinea pigs and mice to helical sequential polymers of amino acids.

The immune responses against the sequential polypeptides; (T-G-A-Gly)n, (T-A-G-Gly)n, (Phe-G-A-Gly)n and (Phe-A-G-Gly)n were studied in inbred guinea pigs and mice. Strain 13 guinea pigs responded to (Phe-G-A-Gly)n and (T-G-A-Gly)n whereas strain 2 guinea pigs responded to (T-A-G-GLY)n and (Phe-A-G-Gly)n. These responses which are linked to MHC, are only against the helical form of the polymers which have conformational determinants. Significant cross reactions at the humoral and T cell levels (PELS) are exhibited with the following reciprocal combinations: (Phe-G-A-Gly)n and (T-G-A-Gly)n; (T-A-G-Gly)n and (Phe-A-G-Gly)n. With mice, the polymers were shown to be T dependent with the following response patterns: mice of H-2b haplotype respond against (T-G-A-Gly)n; those of H-2b, f and r haplotypes respond against (T-A-G-Gly)n. There are no responders against (Phe-G-A-Gly)n and only mice of H-2f respond against (Phe-A-G-Gly)n. "Nonresponders" respond against the MBSA aggregates of all of these polymers. The Ir gene(s) controlling these T cell dependent H-linked responses mapped to the IA subregion. Antibody responses against (T-G-A-Gly) and (T-A-G-Gly) were quite variable, and were most marked in, F1 mice of (responder and nonresponder) and in backcross populations of (F1 x R) and (F1 x NR). However, the T cell proliferative responses performed with nylon wool purified T cells gave clear cut and predictable distinctions between "responders" and nonresponders and linkage with responding haplotype. Hypotheses advanced to explain these findings relate to the poor immunogenicity (antibody) of these polymers, which have a restricted number of repeating determinants, the B cell mitogenic properties of these polymers and the possible involvement of suppressor cells. The specificities of the humoral responses, i.e. cross reactions, were similar to those found in guinea pigs. However, in contrast to the guinea pig studies cross stimulation with structurally related polymers occurred only in those situations where the immunizing and "crossreacting" polymers were both immunogenic in mice of the same haplotype, i.e., (T-A-G-Gly)n and (Phe-A-G-Gly)n in mice of H-2f haplotypes.

Animals↗

PubMed2004

Release of chlorhexidine digluconate and flexural properties of glass fibre reinforced provisional fixed partial denture polymer.

The objective of this study was to determine the flexural properties and the release of chlorhexidine digluconate (CHX) of CHX laced unidirectional E-glass fibre reinforced provisional fixed partial denture polymer. Bar shaped test specimens (3.3 x 10.0 x 65.0 mm) were fabricated from provisional fixed partial denture polymer (mixture of poly[ethylmethacrylate] powder and n-poly[butyl methacrylate] monomer liquid) with E-glass fibre reinforcements. Poly(methyl methacrylate) preimpregnated continuous unidirectional glass fibre reinforcement was laced with CHX. The glass fibre reinforcements were incorporated into the polymer and the polymerised to the form of test specimens. In addition test specimens without CHX in glass fibre reinforcement were made for comparison. Control specimens did not contain glass fibres in the test specimens. Flexural strength and modulus of test specimens (n = 6) was tested with three-point bending test after storing the specimens dry or in water (two weeks). Released CHX was determined with high performance liquid chromatography during 180 days water immersion. In dry conditions, the flexural strength and the modulus of the polymer was 43 MPa and 1.7 GPa, and with glass fibre reinforcement 96 MPa and 3.5 GPa. With the reinforcement laced with CHX, the strength was 92 MPa and the modulus was 3.2 GPa. The water storage of test specimens did not weaken the reinforced polymer. The majority of the CHX released from the glass fibre reinforced polymer during the first days of storage in water. Flexural properties of provisional fixed partial denture polymer were increased using glass fibre reinforcement. The fibre reinforcement that was laced with CHX resulted in similar reinforcing effect.

Adhesives↗

PubMed1982

Identification of alpha-fetoprotein polymers. Artifacts of the isolation procedure.

By combining polyacrylamide gel electrophoresis and radioimmunoassay, a method has been developed to detect polymeric forms of alpha-fetoprotein (AFP) during the isolation procedure. The method is capable of detecting AFP polymers in the presence of other serum proteins in serum samples that contain as little as 100 ng of AFP. Using this method, we have found that AFP polymers do not exist in cord serum; if encountered, we feel they should be considered to be artifacts of the isolation procedure AFP polymers appear in 7.5% polyacrylamide gel as multiple bands. We believe the multiple bands to be AFP polymers and not serum protein contaminants for the following reasons: (1) the electrophoretic pattern is very similar to that of serum albumin; (2) the polymers do exhibit AFP activity, although less than the monomeric form does; (3) the molecular weight of the dimer is exactly twice that of the monomer; (4) in the presence of sodium dodecyl sulfate and mercaptoethanol, the polymers move to the same position as do the monomers in polyacrylamide gel electrophoresis; (5) the polymers cannot be removed by repeated use of an immunoadsorbent affinity column designed to remove contaminant serum proteins.

Biopolymers↗

PubMed1983

Possible treadmilling in zinc(II)-induced sheet polymers of bovine brain microtubule protein.

We have examined the ability of zinc(II)-induced sheet polymers, formed from thrice-cycled bovine brain microtubule protein prepared in the absence of glycerol, to exchange with tubulin subunits at steady state. By a rapid filtration assay in which labeled GTP was used as a marker for tubulin addition and loss, we found that steady-state sheet polymers, formed in 0.5 mM-ZnCl2, 1 mM-dithiothreitol, and 100 mM-2-(N-morpholino)ethanesulfonic acid (pH 6.75) in the presence of a GTP-regenerating system at 37 degrees C, incorporated the label in a time-dependent manner to a maximum level. The steady-state uptake of label was inhibited by colchicine, podophyllotoxin and vinblastine. In pulse-chase experiments, we observed that label added onto sheet polymers in a short pulse was retained for a period equal to that required by the polymers to become fully labeled in a continuous pulse; thereafter, the label was lost gradually to a baseline level. An average of 82% of the label was retained in the sheet polymers after a "cold" chase of equal duration to the time of the pulse. Sheet polymers assembled from microtubule protein prepared in the presence of glycerol gave similar results. Using a double-labeling procedure to analyze tubulin addition and loss simultaneously, we found that the rates of steady-state addition and loss were similar. Sheet polymers retained their structural integrity throughout these experiments, as determined by electron microscopy. We believe that the data are consistent with a "treadmilling" mechanism of polymerization and depolymerization, analogous to that documented to occur in steady-state microtubules in vitro. Such a mechanism is discussed in the context of recent findings from structural studies, and a model consistent with established structural data is offered.

Animals↗

PubMed1989

Optimization of the in vitro packaging efficiency of bacteriophage T7 DNA: effects of neutral polymers.

The in vitro DNA packaging of several DNA bacteriophages is stimulated by the presence of neutral polymers. To optimize bacteriophage T7 DNA packaging and to understand the basis for optimization, the efficiency of T7 DNA packaging has been determined at completion, as a function of the type, molecular mass, and concentration of the polymer added. When the polymer used was polyethylene glycol (PEG) of 0.2, 0.6 or 12.6 kDa, the efficiency of DNA packaging reached maximum at an intermediate concentration of polymer. The osmotic pressure (Pos) at maximum efficiency was either in, or close to, the range of colloid Pos measured for the intact host cell. The optimum Pos increased as the size of the polymer used decreased. PEG-100 (of 0.1 kDa) did not stimulate in vitro T7 DNA packaging. Dextran of 10 kDa also stimulated packaging and produced maximum efficiency at a physiological Pos. The degree of stimulation increases as DNA packaging extract concentration decreases; stimulation by as much as two to three orders of magnitude is observed. The presence of added polymer reduces fluctuations in DNA packaging efficiency caused by variability in the concentration of DNA packaging extracts. For reproducible and high efficiency packaging, the dextran was more reliable than the PEGs, possibly because the Pos of the dextran solutions is less sensitive to polymer concentration than is the Pos of PEG solutions. The optimum concentration of dextran at completion was also the optimum at all times before completion.

Capsid↗

PubMed2006

Natural polymers for gene delivery and tissue engineering.

Although the field of gene delivery is dominated by viral vectors and synthetic polymeric or lipid gene carriers, natural polymers offer distinct advantages and may help advance the field of non-viral gene therapy. Natural polymers, such as chitosan, have been successful in oral and nasal delivery due to their mucoadhesive properties. Collagen has broad utility as gene activated matrices, capable of delivering large quantities of DNA in a direct, localized manner. Most natural polymers contain reactive sites amenable for ligand conjugation, cross-linking, and other modifications that can render the polymer tailored for a range of clinical applications. Natural polymers also often possess good cytocompatibility, making them popular choices for tissue engineering scaffolding applications. The marriage of gene therapy and tissue engineering exploits the power of genetic cell engineering to provide the biochemical signals to influence proliferation or differentiation of cells. Natural polymers with their ability to serve as gene carriers and tissue engineering scaffolds are poised to play an important role in the field of regenerative medicine. This review highlights the past and present research on various applications of natural polymers as particulate and matrix delivery vehicles for gene delivery.

Animals↗

PubMed2004

Imprinted polymer layer for recognizing double-stranded DNA.

A method of preparing a thin polymer layer able to recognize double-stranded DNA (dsDNA) was developed by using 2-vinyl-4,6-diamino-1,3,5-triazine (VDAT) as a functional monomer for creating a DNA-imprinted polymer. The formation of hydrogen bonds between VDAT and A-T base pairs in dsDNA was confirmed by measuring the effects of VDAT on the melting point and the NMR and CD spectra of dsDNA. An imprinted polymer that can recognize dsDNA of the verotoxin gene was prepared by polymerizing VDAT, acrylamide, a crosslinking agent, and the template verotoxin dsDNA on a silanized glass surface. The specificity of this polymer layer for binding verotoxin dsDNA was investigated by using fluorescent-labelled dsDNAs. The fluorescence intensity of the polymer layer after binding verotoxin dsDNA was twice as high as after binding oligo(dG)-oligo(dC), indicating that verotoxin dsDNA was preferentially bound to the polymer imprinted with verotoxin dsDNA. The kinetics of verotoxin dsDNA binding to the imprinted polymer were analyzed by surface plasmon resonance measurements. The dissociation constant (KD) was low, of the order of 10(-9)M.

Acrylic Resins↗

PubMed2006

Comblike poly(ethylene oxide)/hydrophobic C6 branched chitosan surfactant polymers as anti-infection surface modifying agents.

A series of structurally well-defined poly(ethylene oxide)/hydrophobic C6 branched chitosan surfactant polymers that undergo surface induced self assembly on hydrophobic biomaterial surfaces were synthesized and characterized. The surfactant polymers consist of low molecular weight (Mw) chitosan backbone with hydrophilic poly(ethylene oxide) (PEO) and hydrophobic hexyl pendant groups. Chitosan was depolymerized by nitrous acid deaminative cleavage. Hexanal and aldehyde-terminated PEO chains were simultaneously attached to low Mw chitosan hydrochloride via reductive amination. The surfactant polymers were prepared with various ratios of the two side chains. The molecular composition of the surfactant polymers was determined by FT-IR and 1H NMR. Surface active properties at the air-water interface were determined by Langmuir film balance measurements. The surfactant polymers with PEO/hexyl ratios of 1:3.0 and 1:14.4 were used as surface modifying agents to investigate their anti-infection properties. E. coli adhesion on Silastic surface was decreased significantly by the surfactant polymer with PEO/hexyl 1:3.0. Surface growth of adherent E. coli was effectively suppressed by both tested surfactant polymers.

Adhesins, Bacterial↗

PubMed2006

Surface modification on microfluidic devices with 2-methacryloyloxyethyl phosphorylcholine polymers for reducing unfavorable protein adsorption.

Surface modification of polymer materials for preparing microfluidic devices including poly(dimethyl siloxane) (PDMS) was investigated with phospholipids polymers such as poly(2-methacryloyloxylethyl phosphorylcholine(MPC)-co-n-butyl methacrylate) (PMB) and poly(MPC-co-2-ethylhexyl methacrylate-co-2-(N,N-dimethylamino)ethyl methacrylate) (PMED). The hydrophilicity of every surface on the polymer materials modified with these MPC polymers increased and the value of zeta-potential became close to zero. The protein adsorption on the polymer materials with and without the surface modification was evaluated using a protein mixture of human plasma fibrinogen and serum albumin. Amount of proteins adsorbed on these polymeric materials showed significant reduction by the surface modification with the MPC polymers compared to the uncoated surfaces ranging from 56 to 90%. Furthermore, we successfully prepared PDMS-based microchannel which was modified by simple coating with the PMB and PMED. The modified microchannel also revealed a significant reduction of adsorption of serum albumin. We conclude that the MPC polymers are useful for reducing unfavorable protein adsorption on microfluidic devices.

Adsorption↗

PubMed2005

The static strength and modulus of fiber reinforced denture base polymer.

OBJECTIVES: Partial fiber reinforcements have been employed to strengthen dentures both during repair and in the manufacturing process. The reinforcing fibers can be evenly distributed in the denture base polymer or alternatively fiber-rich phase in the denture base polymer can form a separate structure. The aim of this study was to determinate static three-point flexural strength and modulus of denture base polymer that had been reinforced with different fiber reinforcements. METHODS: The test specimens (3 x 5 x 50 mm) were made of auto-polymerized denture base polymer and reinforced with different fiber reinforcements. The test groups were: (A) no fibers; (B) non-impregnated polyethylene fibers; (C) light-polymerized monomer impregnated glass fibers; (D) porous polymer preimpregnated glass fibers and (E) light-polymerized monomer-polymer impregnated glass fibers. The fibers were oriented parallel to the long axis of the specimen and embedded into the denture base resin on the compression side (n=7) or tension side (n=7). Dry specimens were tested with three-point static flexural strength test set-up at crosshead speed of 5 mm/min. RESULTS: The statistical analysis by two-way analysis of variance showed that the brand and the location of the fiber reinforcements significantly influenced the flexural strength (p<0.0001). However, the location of the fiber reinforcements did not influence the flexural modulus (p<0.722). SIGNIFICANCE: The results suggest that impregnated and preimpregnated fibers reinforce denture base polymer more than non-impregnated fibers. Fiber reinforcements placed on the tensile side resulted in considerably higher flexural strength and flexural modulus values compared with same quantity of fibers placed on the compression side.

Acrylic Resins↗

PubMed2004

The characteristics of spontaneously forming physically cross-linked hydrogels composed of two water-soluble phospholipid polymers for oral drug delivery carrier I: hydrogel dissolution and insulin release under neutral pH condition.

Hydrogels bearing a phospholipid polar group, 2-methacryloyloxyethyl phosphorylcholine (MPC), were prepared from two aqueous solutions of polymers, water-soluble poly[MPC-co-methacrylic acid (MA)] (PMA) and poly[MPC-co-n-butyl methacrylate (BMA)] (PMB). The hydrogel, which was formed by physical cross-linking spontaneously without any chemical reactions and/or any physical stimuli, showed a controllable insulin release through a pH change in the medium by changing the hydrogen bonds. In this study, the mechanical strength, erosion of the hydrogel caused by polymer dissociation, and the release of insulin were examined with attention to the following three parameters of the MPC polymer: molecular weight of the polymers, composition of PMA and PMB (PMA/PMB ratio), and polymer concentration inside the hydrogel. The hydrogel with the highest mechanical strength was obtained at a PMA/PMB ratio = 3/7 (v/v, by volume ratio) while the hydrogel with the slowest dissolution was obtained at a ratio of 5/5 (v/v). The release was in good match with the dissolution and followed anomalous transport for all, but the diffusion exponent n changed according to the PMA/PMB ratio. An increase in the polymer concentration inside the hydrogel caused an increase in the mechanical strength of the hydrogel. When the polymer concentration was more than 20 wt.%, the absorption of water under neutral pH condition (pH 6.8) was observed. The release of insulin was suppressed below 10% during the swelling process of the hydrogel under neutral pH condition, while release was accelerated during the erosion process of the hydrogel. The relationship between erosion of the hydrogel and the release of the insulin depended on the erosion process of the hydrogel but differed according to the PMA/PMB ratio.

Administration, Oral↗

PubMed2005

The influence of the adsorbent amount on the changes in molecular mass distribution of polymers under adsorption from mixtures.

Changes in the molecular mass distribution (MMD) for polymer as a result of adsorption from binary and ternary solutions have been studied by the exclusion chromatography method. It was found that the affinity of polymer components to a surface has a crucial influence on the changes in MMD of polymers. The diminution of polydispersity in solutions after adsorption was observed for two polymers. In the case of the polar polymer poly(butyl methacrylate) (PBMA) the diminution of polydispersity is caused mainly by the preferential adsorption of low-molecular-mass fractions, whereas in the case of the nonpolar polymer polystyrene (PS) it is caused by the transition of the high-molecular-mass fractions onto the adsorbent surface. The analysis of experimental results indicates that the quantity of the adsorbent affects the composition of the adsorption layer formed by polymers of different chemical nature.

Journal Article↗

PubMed2005

Effects of vinyl series polymers on the formation of hematite particles in a forced hydrolysis reaction.

The influence of polymers on the formation of hematite particles from forced hydrolysis of acidic FeCl(3) solution was investigated using vinyl series polymers with different functional groups. The disk-like hematite particles were produced from forced hydrolysis of acidic FeCl(3) solution in the presence of polyvinyl alcohol (PVA: 0-1 wt%). On the other hand, spherical particles were produced by addition of very small amounts of polyacrylamide (PAAm: 0-0.004 wt%). The size of spherical particles was slightly decreased with increase in the concentration of PAAm. The ellipsoidal particles were precipitated by addition of a very low concentration of polyacrylic acid (PAAc: 0-0.004 wt%). The effect of polymers on the hematite particle formation was expressed in the order of PVA<PAAm<PAAc that is in the reverse order from their average molecular weight. Therefore it was concluded that the effects of polymer molecules strongly depend on the functional groups of polymers. The secondary reduction steps of the concentration of Fe(3+) ions ([Fe]) were observed during aging. This secondary step of [Fe] corresponded to the time of the complete phase transformation from beta-FeOOH to hematite. Thus one was forced to conclude that the dissolution of beta-FeOOH particles is a rate-determining step in the reaction sequence for the systems with polymers. A rotational particle preparation procedure suggested that the morphology of hematite particle is governed by the mode and strength of polymer adsorption onto beta-FeOOH and polynuclear primary particles.

Journal Article↗

PubMed2005

Relaxation phenomena of hydrolyzed polyvinylamine molecules adsorbed at the silica/water interface I. Saturated homogeneous polymer layers.

Surface area exclusion chromatography was used to investigate the adsorption and reconformation characteristics of hydrolyzed polyvinylamine molecules at silica/water interfaces employing radiolabeled polymers. The polymer solution was injected at the inlet of the column, whereas the polymer was successively adsorbed on the stacked glass-fiber filters constituting the stationary phase of the column. The filters and effluent samples collected at the outlet were individually analyzed for radioactivity content, which provided the adsorption histogram and the relative affinity of the various polymers. For saturated polymer layers, the relaxation process was demonstrated when the exceedingly adsorbed molecules desorbed. Modifications in the adsorption on the successive filters were thus converted into changes in the interfacial area of adsorbed molecules, taking into account the deviation from the plateau adsorption expected for nonrelaxing systems. Adsorption characteristics of nonrelaxed polymer layers were determined from the adsorption values determined before relaxation occurred. Adsorption and relaxation characteristics were determined to depend strongly on molecular weight and degree of hydrolysis of the polyvinylamine molecules. Half-hydrolyzed polymers had adsorption and relaxation characteristics close to those of the fully hydrolyzed polyvinylamine. Accordingly, adsorption isotherms on the cellulose/water interface were carried out to possibly extend the main conclusions of the study.

Journal Article↗

PubMed1989

Calculations of scattered light from rigid polymers by Shifrin and Rayleigh-Debye approximations.

We show that the commonly used Rayleigh-Debye method for calculating light scattering can lead to significant errors when used for describing scattering from dilute solutions of long rigid polymers, errors that can be overcome by use of the easily applied Shifrin approximation. In order to show the extent of the discrepancies between the two methods, we have performed calculations at normal incidence both for polarized and unpolarized incident light with the scattering intensity determined as a function of polarization angle and of scattering angle, assuming that the incident light is in a spectral region where the absorption of hemoglobin is small. When the Shifrin method is used, the calculated intensities using either polarized or unpolarized scattered light give information about the alignment of polymers, a feature that is lost in the Rayleigh-Debye approximation because the effect of the asymmetric shape of the scatterer on the incoming polarized electric field is ignored. Using sickle hemoglobin polymers as an example, we have calculated the intensity of light scattering using both approaches and found that, for totally aligned polymers within parallel planes, the difference can be as large as 25%, when the incident electric field is perpendicular to the polymers, for near forward or near backward scattering (0 degrees or 180 degrees scattering angle), but becomes zero as the scattering angle approaches 90 degrees. For randomly oriented polymers within a plane, or for incident unpolarized light for either totally oriented or randomly oriented polymers, the difference between the two results for near forward or near backward scattering is approximately 15%.

Biopolymers↗