Fibrillar Morphology Research Articles

Double/single phase segregation and vertical stratification induced by crystallization in all‐crystalline tri/diblock copolymers and homopolymer blends of poly(3‐hexylthiophene) and poly(ethylene glycol)

Distinct stratified and non‐stratified morphologies were developed in poly(3‐hexylthiophene) (P3HT) and poly(ethylene glycol) (PEG)‐based homopolymer blends and diblock and triblock copolymer systems. By applying X‐ray photoelectron spectroscopy, only a double‐percolation mechanism including assembling of P3HT chains into the nanofibers in solution aging process with a marginal solvent like p‐xylene as well as crystallization of PEG phase in the cast thin films resulted in vertical stratification and networked fibrils. In cast thin films whose PEG phase, due to low molecular weight or being constrained between two rigid P3HT blocks in triblock copolymers was not crystallized, a non‐stratified discrete fibrillar morphology was acquired. Crystallization of PEGs in the thin films mainly participated in networking and expelling pre‐organized P3HT fibrils to the film surface. By performing the solution aging step in a good solvent such as o‐dichlorobenzene, the P3HTs remained in a coily‐like conformation, and casting the corresponding thin films reflected the non‐stratified discrete granular and featureless morphologies. Assembling the P3HT chains in the presence of PEG phase in cast films at most led to the low‐crystalline granules instead of highly crystalline nanofibrils. No significant crystallization in either homopolymer blends or block copolymer systems conduced to a featureless morphology with homogeneous distribution of existed materials. The surface morphology and ordering in various morphologies were studied employing atomic force microscopy, grazing incidence X‐ray diffraction, and ultraviolet–visible analyses. Copyright © 2016 John Wiley & Sons, Ltd.

Insights into amyloid-like aggregation of H2 region of the C-terminal domain of nucleophosmin

Nucleophosmin (NPM1) is a multifunctional protein involved in a variety of biological processes including the pathogenesis of several human malignancies and is the most frequently mutated gene in Acute Myeloid Leukemia (AML). To deepen the role of protein regions in its biological activities, lately we reported on the structural behavior of dissected C-terminal domain (CTD) helical fragments. Unexpectedly the H2 (residues 264–277) and H3 AML-mutated regions showed a remarkable tendency to form amyloid-like assemblies with fibrillar morphology and β-sheet structure that resulted as toxic when exposed to human neuroblastoma cells. More recently NPM1 was found to be highly expressed and toxic in neurons of mouse models of Huntington's disease (HD). Here we investigate the role of each residue in the β-strand aggregation process of H2 region of NPM1 by performing a systematic alanine scan of its sequence and structural and kinetic analyses of aggregation of derived peptides by means of Circular Dichorism (CD) and Thioflavin T (Th-T) assay. These solution state investigations pointed out the crucial role exerted by the basic amyloidogenic stretch of H2 (264–271) and to shed light on the initial and main interactions involved in fibril formation we performed studies on fibrils deriving from the related Ala peptides through the analysis of fibrils with birefringence of polarized optical microscopy and wide-angle X-ray scattering (WAXS). This analysis suggested that the presence of branched Ile269 conferred preferential packing patterns that, instead, appeared geometrically hampered by the aromatic side-chain of Phe268. Present investigations could be useful to deepen the knowledge of AML molecular mechanisms and the role of cytoplasmatic aggregates of NPM1c+.

Studies on Syndiotactic Polystyrene/Poly(3‐hexyl thiophene) Composite

SummarySyndiotactic polystyrene (sPS) generally exhibits five crystal modifications (α, β, γ, δ and ϵ) with different molecular conformations and also with different chain packing structures. Among these modifications, the δ phase of sPS is very promising as it absorbs guest molecules producing clathrate or intercalate co‐crystals of sPS. In this connection, sPS/poly(3‐hexyl thiophene) (P3HT) composites have been prepared with the expectation of formation of P3HT nano‐crystal in the crystalline lattice of sPS. Composites have been characterized by UV‐Vis, XRD, TGA studies. Mechanical and morphological properties have been explored. UV spectra show the appearance of vibronic structure of P3HT even at low concentration of P3HT, indicating the formation of nanoaggregates of P3HT in the sPS matrix. FESEM and HRTEM analysis reveal the formation of fibrillar morphology of composites and EDX studies indicate the presence of P3HT in the fiber as well as the interaction between sPS and P3HT. There is enhancement of diameter of sPS/P3HT fibers as well as increase of mechanical strength of fibers.

Modulation of the Excited-State Dynamics of 2,2'-Bipyridine-3,3'-diol in Crown Ethers: A Possible Way To Control the Morphology of a Glycine Fibril through Fluorescence Lifetime Imaging Microscopy.

In this article, we have investigated the modulation of excited-state intramolecular double proton transfer (ESIDPT) dynamics of 2,2'-bipyridine-3,3'-diol (BP(OH)2) in two crown ethers (CEs), namely, 18-Crown-6 (18C6) and 15-Crown-5 (15C5). From steady-state UV-visible measurements, we have shown that there is no significant interaction between the dienol tautomeric form of BP(OH)2 and two CEs. However, in the presence of CEs, an additional emission band (∼415 nm) is generated along with the diketo tautomer band (∼465 nm). In time-resolved analysis, we have observed the generation of ∼260 ps rise component in the presence of 18C6. Therefore, by combining the results of steady-state and time-resolved emissions, we have proposed that the water-assisted ESIDPT route of BP(OH)2 generates a hydronium ion (H3O+) in the excited state. 18C6 binds nicely to this H3O+ ion. As a result, retarded ESIDPT dynamics is observed in 18C6. However, as 15C5 cannot bind H3O+ properly, no rise component is found. With the addition of potassium chloride (KCl), the contribution of the rise component decreases due to unavailability of free 18C6 cavity to capture the H3O+ ion generated in the excited state. Addition of calcium chloride (CaCl2) leads to complete removal of the rise component due to the inhibition of the water-assisted ESIDPT route. From wavelength-dependent behavior, we have observed that the rise component is present only at 465 nm in 18C6. We have also shown that the fibrillar morphology of glycine can be successfully probed through fluorescence lifetime imaging microscopy using BP(OH)2 as an imaging agent. Modulation of fibrillar morphology has been found in the presence of two CEs. The interaction of glycine fiber with CEs can be explained by lifetime distribution analysis.

Distinct C9orf72-Associated Dipeptide Repeat Structures Correlate with Neuronal Toxicity.

Hexanucleotide repeat expansions in C9orf72 are the most common inherited cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). The expansions elicit toxicity in part through repeat-associated non-AUG (RAN) translation of the intronic (GGGGCC)n sequence into dipeptide repeat-containing proteins (DPRs). Little is known, however, about the structural characteristics and aggregation propensities of the dipeptide units comprising DPRs. To address this question, we synthesized dipeptide units corresponding to the three sense-strand RAN translation products, analyzed their structures by circular dichroism, electron microscopy and dye binding assays, and assessed their relative toxicity when applied to primary cortical neurons. Short, glycine-arginine (GR)3 dipeptides formed spherical aggregates and selectively reduced neuronal survival compared to glycine-alanine (GA)3 and glycine-proline (GP)3 dipeptides. Doubling peptide length had little effect on the structure of GR or GP peptides, but (GA)6 peptides formed β-sheet rich aggregates that bound thioflavin T and Congo red yet lacked the typical fibrillar morphology of amyloids. Aging of (GA)6 dipeptides increased their β-sheet content and enhanced their toxicity when applied to neurons. We also observed that the relative toxicity of each tested dipeptide was proportional to peptide internalization. Our results demonstrate that different C9orf72-related dipeptides exhibit distinct structural properties that correlate with their relative toxicity.

3D texture analysis for classification of second harmonic generation images of human ovarian cancer.

Remodeling of the collagen architecture in the extracellular matrix (ECM) has been implicated in ovarian cancer. To quantify these alterations we implemented a form of 3D texture analysis to delineate the fibrillar morphology observed in 3D Second Harmonic Generation (SHG) microscopy image data of normal (1) and high risk (2) ovarian stroma, benign ovarian tumors (3), low grade (4) and high grade (5) serous tumors, and endometrioid tumors (6). We developed a tailored set of 3D filters which extract textural features in the 3D image sets to build (or learn) statistical models of each tissue class. By applying k-nearest neighbor classification using these learned models, we achieved 83–91% accuracies for the six classes. The 3D method outperformed the analogous 2D classification on the same tissues, where we suggest this is due the increased information content. This classification based on ECM structural changes will complement conventional classification based on genetic profiles and can serve as an additional biomarker. Moreover, the texture analysis algorithm is quite general, as it does not rely on single morphological metrics such as fiber alignment, length, and width but their combined convolution with a customizable basis set.

Phototriggered Supramolecular Polymerization.

Photo-initiated supramolecular polymerization of a naphthalenediimide (NDI-1) derivative containing an ortho-nitrobenzyl (ONB)-protected amide group is demonstrated. In a hydrocarbon solvent (methylcyclohexane), it remains as monomer. Upon photo-irradiation, deprotection of the ONB group produces NDI-2 with a free amide group, which drives supramolecular polymerization by self-complementary H-bonding between the amide groups, leading to gelation. The polymerization rate can be controlled by tuning the energy of the light source. During photopolymerization, a gradual increase in hydrodynamic radius and viscosity is noticed. More interestingly, the morphology of the supramolecular polymer of NDI-2, produced by photo-irradiation, was a spherulite, which is in sharp contrast with the fibrillar morphology of NDI-2 polymer, when assembled spontaneously without a phototrigger. This is ascribed to the ability of the ONB-caged pro-monomer (NDI-1) to act as a chain-stopper by forming a H-bonded complex with the active monomer during the growth of the supramolecular polymer under photo-irradiation.

Nanoporous-crystalline poly(2,6-dimethyl-1,4-phenylene)oxide (PPO) aerogels

Abstract Monolithic aerogels of poly(2,6-dimethyl-1,4-phenylene)oxide (an industrially relevant polymer generally known as polyphenyleneoxide or PPO), have been prepared and characterized. These aerogels obtained by supercritical carbon dioxide extraction of thermoreversible gels of high molecular weight PPO present an apparent porosity typically in the range 70%–95% and high surface area values up to 750 m 2 /g. Moreover these aerogels are characterized by an excellent sorption uptake of organic pollutants at low vapor pressure and good recyclability by thermal regeneration. Good mechanical properties and dimensional stability of PPO monoliths is due to the polymer high molecular weight which ensures formation of a fibrillar morphology, already in the precursor gel. Sorption capacity and recyclability of PPO aerogels are mostly due to their crystalline phase: (i) its nanoporous-crystalline structure assures high specific surface areas; (ii) its high melting temperature assures a high thermal monolith stability as well as easy and cheap recovery of absorbed guest molecules by thermal treatments rather than by solvent extractions.

Hierarchical nanostructured polyaniline functionalized graphene/poly(vinylidene fluoride) composites for improved dielectric performances

Abstract Hierarchical nanostructured polymeric dielectric composites (PGP) based on semicrystalline poly (vinylidene fluoride) (PVDF) matrix are fabricated by incorporating polyaniline-grafted-graphene oxide (G-graft-PANI). HR-TEM images show uniform dispersion of GO within PVDF matrix. FE-SEM micrographs of PGP composites indicate fibrillar morphology produced from supramolecular organization of G-graft-PANI with PVDF chains resulting hierarchical nanostructure. The dipolar interaction between the filler and PVDF is established from FTIR spectra and Raman spectroscopy indicates reduction of GO during fabrication process. The interaction ability and high surface area of G-graft-PANI cause nonpolar α-phase PVDF to polar β-phase transformation to 91% for 5 wt% filler. PGP composites show higher melting and crystallization temperatures. It exhibit spectacular increase of dielectric permittivity, dielectric loss, and dc-conductivity relative to that of neat PVDF films. The values of dielectric permittivity and dielectric loss are 264 and 1.125 at 102 Hz frequency and dc-conductivity increases 8 orders from that of pristine PVDF for loading of 5% G-graft-PANI.

Automated Analysis of Orientational Order in Images of Fibrillar Materials

Nanofibers are a ubiquitous structural motif in a variety of functional materials. In the field of organic electronics, π–π-stacking of conjugated polymers leads to fibrillar morphologies with a wide array of fiber packing behavior. Fiber orientation and alignment are known to influence the charge transport properties of devices such as organic field effect transistors. The solution processing methods used to create these devices give rise to large variations in these structural parameters—however, they are only observable with imaging techniques such as atomic force microscopy (AFM). To bring more rigorous quantification of orientation and alignment to these materials, a comprehensive image analysis tool is introduced to quantify the two-dimensional orientation and alignment of nanofibers from AFM images. It has been developed in MATLAB and packaged as a stand-alone application, so that researchers with no computational expertise can produce publication-ready figures directly from their images. AFM frequ...

Mechanical properties and stress-induced polymorphic transformations of blends of random isotactic propylene-1-hexene copolymers

Abstract The mechanical properties of binary blends of propylene-1-hexene random copolymers (with 11 and 21 mol% 1-hexene) are studied in parallel with polymorphic transformations under uniaxial tensile deformation. The modulus, yield stress, and draw ratio of the pure PH copolymers decrease with increasing 1-hexene content, while for the blends the change of mechanical properties with composition is highly non-linear. The addition of just 10 wt % PH11 to PH21 doubles the elastic modulus and yield strength of the blends in reference to the value of PH21, reaching for all blends values close to the performance of pure PH11. The elongation at break and the ultimate tensile strength increase more gradually with content of PH11. On tensile deformation, pure components and blends undergo morphological and polymorphic transformations, such as a reversible lamellar to fibrillar transformation of trigonal PH21, or an irreversible α crystal to mesophase in pure PH11 and the blends. In blends and neat PH11, a fibrillar trigonal morphology that develops under deformation is stabilized by the transformation of α to mesophase, and remains after removing the load, explaining the lower elastic recovery of the blends compared to PH21. The formation of stress-induced trigonal crystallites in PH11 and blends after strains >150% is explained as a decrease of the free energy barrier for nucleation of a phase that requires short iPP sequences.

Novel cellulose-collagen blend biofibers prepared from an amine/salt solvent system

Cellulose/collagen biofibers were produced from ethylene diamine/potassium thiocyanate binary solvent system, with methanol as a coagulant. The dynamic viscosity of the solutions decreased with the gradual increase in the collagen content up to 40%. The elemental analysis showed incorporation of collagen into cellulose matrix, thereby demonstrating some degree of interaction with the cellulose matrix. The chemical and thermal analysis further revealed an intermolecular interaction between cellulose and the protein and improved thermal stability, respectively. Furthermore, the electron microscopy images mostly exhibited fibrillar morphology with no visible phase separation, indicating compatibility between the two phases. Moreover, biofibers containing higher cellulose content showed higher crystallinity, tensile, and birefringence properties of the composite fibers.

A Detailed Analysis of the Morphology of Fibrils of Selectively Mutated Amyloid β (1-40).

A small library of rationally designed amyloid β [Aβ(1-40)] peptide variants is generated, and the morphology of their fibrils is studied. In these molecules, the structurally important hydrophobic contact between phenylalanine 19 (F19) and leucine 34 (L34) is systematically mutated to introduce defined physical forces to act as specific internal constraints on amyloid formation. This Aβ(1-40) peptide library is used to study the fibril morphology of these variants by employing a comprehensive set of biophysical techniques including solution and solid-state NMR spectroscopy, AFM, fluorescence correlation spectroscopy, and XRD. Overall, the findings demonstrate that the introduction of significant local physical perturbations of a crucial early folding contact of Aβ(1-40) only results in minor alterations of the fibrillar morphology. The thermodynamically stable structure of mature Aβ fibrils proves to be relatively robust against the introduction of significantly altered molecular interaction patterns due to point mutations. This underlines that amyloid fibril formation is a highly generic process in protein misfolding that results in the formation of the thermodynamically most stable cross-β structure.

Composite Hydrogels with Tunable Anisotropic Morphologies and Mechanical Properties

Fabrication of anisotropic hydrogels exhibiting direction-dependent structure and properties has attracted great interest in biomimicking, tissue engineering, and bioseparation. Herein, we report a freeze-casting-based fabrication of structurally and mechanically anisotropic aerogels and hydrogels composed of hydrazone cross-linked poly(oligoethylene glycol methacrylate) (POEGMA) and cellulose nanocrystals (CNCs). We show that, by controlling the composition of the CNC/POEGMA dispersion and the freeze-casting temperature, aerogels with fibrillar, columnar, or lamellar morphologies can be produced. Small-angle X-ray scattering experiments show that the anisotropy of the structure originates from the alignment of the mesostructures, rather than the CNC building blocks. The composite hydrogels show high structural and mechanical integrity and a strong variation in Young’s moduli in orthogonal directions. The controllable morphology and hydrogel anisotropy, coupled with hydrazone cross-linking and biocompatib...

Effect of Isotacticity of Linear Poly(N-isopropylacrylamide) on its Gelation in Benzyl Alcohol

Thermoreversible gelation of three different isotactic linear poly(N-isopropylacrylamide) (PNIPAM)s having meso dyad (m) values 62, 68 and 81% has been observed in benzyl alcohol. All the gels were transparent in nature. SEM image of the dried gels showed fibrillar network morphology. Melting temperature of the gels gradually increased with the increase in the concentration. XRD data of dry polymers and their corresponding dry gels showed shifting in the peak positions. Rheological study showed that stronger gels were formed with increasing isotacticity of PNIPAM while lower isotactic sample exhibited typical polymer melt rheology. The formation of a plunge in the storage modulus as well as in the viscosity plot at the same frequency range indicates the reversible nature of the structure breaking/reformation under frequency sweep. Moreover, the mechanical strength of the gel decreased with increase in temperature. UV-Vis kinetic study also indicated the change in the conformation and aggregation of PNIPAM chains during gelation. Molecular modelling calculation showed that the number of solvent molecules involved in forming gel (polymer-solvent compound) decreased with the increase in the isotacticity of the polymer. Gelation rate of these gels was studied as a function of temperature, concentration and isotacticity using test-tube tilting method. It increased with the increase in the concentration and isoacticity of the polymer, and with the decrease in the temperature. Critical gelation concentration of the gel gradually increased with the decrease in the isotacticity and with the increase in the temperature. All these experimental results indicated that gelation occurs presumably through polymer-solvent compound formation. Thermoreversible gelation of different isotactic [meso diad (m) = 62, 68 and 81%] linear poly(N-isopropylacrylamide) (PNIPAM)s has been observed in benzyl alcohol. Gelation rate depends on temperature, concentration, and isotacticity of PNIPAM. SEM, XRD, rheology and UV-Vis studies, and molecular modelling support its formation presumably via polymer-solvent compound formation.

Aggregation of Trp > Glu point mutants of human gamma-D crystallin provides a model for hereditary or UV-induced cataract.

Numerous mutations and covalent modifications of the highly abundant, long-lived crystallins of the eye lens cause their aggregation leading to progressive opacification of the lens, cataract. The nature and biochemical mechanisms of the aggregation process are poorly understood, as neither amyloid nor native-state polymers are commonly found in opaque lenses. The βγ-crystallin fold contains four highly conserved buried tryptophans, which can be oxidized to more hydrophilic products, such as kynurenine, upon UV-B irradiation. We mimicked this class of oxidative damage using Trp→Glu point mutants of human γD-crystallin. Such substitutions may represent a model of UV-induced photodamage-introduction of a charged group into the hydrophobic core generating "denaturation from within." The effects of Trp→Glu substitutions were highly position dependent. While each was destabilizing, only the two located in the bottom of the double Greek key fold-W42E and W130E-yielded robust aggregation of partially unfolded intermediates at 37°C and pH 7. The αB-crystallin chaperone suppressed aggregation of W130E, but not W42E, indicating distinct aggregation pathways from damage in the N-terminal vs C-terminal domain. The W130E aggregates had loosely fibrillar morphology, yet were nonamyloid, noncovalent, showed little surface hydrophobicity, and formed at least 20°C below the melting temperature of the native β-sheets. These features are most consistent with domain-swapped polymerization. Aggregation of partially destabilized crystallins under physiological conditions, as occurs in this class of point mutants, could provide a simple in vitro model system for drug discovery and optimization.

Clues for divergent, polymorphic amyloidogenesis through dissection of amyloid forming steps of bovine carbonic anhydrase and its critical amyloid forming stretch

Certain amino acid stretches are considered ‘critical’ to trigger amyloidogenesis in a protein. Synthetic peptides corresponding to these stretches are often used as experimental mimics for studying the amyloidogenesis of their parent protein. Here we provide evidence that such simple extrapolation is misleading. We scrutinized each step of amyloid progression of full length bovine carbonic anhydrase (BCA) and compared it with the amyloidogenic process of its critical peptide stretch 201–227 (PepB). We found that under similar solution conditions amyloidogenesis of BCA followed surface-catalyzed secondary nucleation, whereas, that of PepB followed classical nucleation-dependent pathway. AFM images showed that while BCA formed short, thick and branched fibrils, PepB formed thin, long and unbranched fibrils. Structural information obtained by ATR-FTIR spectroscopy suggested parallel arrangement of intermolecular β-sheet in BCA amyloids in contrast to PepB amyloids which arranged into antiparallel β sheets. Amyloids formed by BCA were unable to seed the fibrillation of PepB and vice versa. Even the intermediates formed during lag phase revealed contrasting FTIR and far UV CD signature, hydrophobicity, morphology and cell cytotoxicity. Thus, we propose that sequences other than critical amyloidogenic stretches may significantly influence the initiation, polymerization and final fibrillar morphology of amyloid forming protein. The results have been discussed in light of primary sequence mediated amyloid polymorphism and its importance in the rational design of amyloid nanomaterials possessing desired physico-chemical properties.

Antimicrobial peptide (Cn-AMP2) from liquid endosperm of Cocos nucifera forms amyloid-like fibrillar structure.

Cn-AMP2 is an antimicrobial peptide derived from liquid endosperm of coconut (Cocos nucifera). It consists of 11 amino acid residues and predicted to have high propensity for β-sheet formation that disposes this peptide to be amyloidogenic. In the present study, we have examined the amyloidogenic propensities of Cn-AMP2 in silico and then tested the predictions under in vitro conditions. The in silico study revealed that the peptide possesses high amyloidogenic propensity comparable with Aβ. Upon solubilisation and agitation in aqueous buffer, Cn-AMP2 forms visible aggregates that display bathochromic shift in the Congo red absorbance spectra, strong increase in thioflavin T fluorescence and fibrillar morphology under transmission electron microscopy. All these properties are typical of an amyloid fibril derived from various proteins/peptides including Aβ.

Self-Assembly of Telechelic Tyrosine End-Capped PEO and Poly(alanine) Polymers in Aqueous Solution.

The self-assembly in aqueous solution of three novel telechelic conjugates comprising a central hydrophilic polymer and short (trimeric or pentameric) tyrosine end-caps has been investigated. Two of the conjugates have a central poly(oxyethylene) (polyethylene oxide, PEO) central block with different molar masses. The other conjugate has a central poly(L-alanine) (PAla) sequence in a purely amino-acid based conjugate. All three conjugates self-assemble into β-sheet based fibrillar structures, although the fibrillar morphology revealed by cryogenic-TEM is distinct for the three polymers--in particular the Tyr5-PEO6k-Tyr5 forms a population of short straight fibrils in contrast to the more diffuse fibril aggregates observed for Tyr5-PEO2k-Tyr5 and Tyr3-PAla-Tyr3. Hydrogel formation was not observed for these samples (in contrast to prior work on related systems) up to quite high concentrations, showing that it is possible to prepare solutions of peptide-polymer-peptide conjugates with hydrophobic end-caps without conformational constraints associated with hydrogelation. The Tyr5-PEO6k-Tyr5 shows significant PEO crystallization upon drying in contrast to the Tyr5-PEO2k-Tyr5 conjugate. Our findings point to the remarkable ability of short hydrophobic peptide end groups to modulate the self-assembly properties of polymers in solution in model peptide-capped "associative polymers". Retention of fluidity at high conjugate concentration may be valuable in potential future applications of these conjugates as bioresponsive or biocompatible materials, for example exploiting the enzyme-responsiveness of the tyrosine end-groups.

Hydration of water- and alkali-activated white Portland cement pastes and blends with low-calcium pulverized fuel ash

Pastes of white Portland cement (wPc) and wPc-pulverized fuel ash (pfa) blends were studied up to 13years. The reaction of wPc with water was initially retarded in the presence of pfa particles but accelerated at intermediate ages. Reaction with KOH solution was rapid with or without pfa. A universal compositional relationship exists for the C-A-S-H in blends of Pc with aluminosilicate-rich SCMs. The average length of aluminosilicate anions increased with age and increasing Al/Ca and Si/Ca; greater lengthening in the blends was due to additional Al3+ at bridging sites. The morphology of outer product C-A-S-H was always foil-like with KOH solution, regardless of chemical composition, but with water it had fibrillar morphology at high Ca/(Si+Al) ratios and foil-like morphology started to appear at Ca/(Si+Al) ≈1.2–1.3, which from the literature appears to coincide with changes in the pore solution. Foil-like morphology cannot be associated with entirely T-based structure.