Lamella-forming Diblock Copolymers Research Articles

Distinctive Dielectric Permittivity of Hierarchical Nanostructures with Ordered Nanoparticle Networks Self-Assembled from AB-g-NP/AC Block Copolymer Mixtures.

Directing nanoparticles into ordered organization in polymer matrix to improve macroscopic properties of nanocomposites remains a challenge. Herein, by means of theoretical simulations, we show the high permittivity of hybrid nanostructures designed with mixtures of AB block copolymer-grafted nanoparticles and lamella-forming AC diblock copolymers. The grafted nanoparticles self-assemble into parallel stripes or highly ordered networks in the lamellae of the AC diblock copolymers. The ordered nanoparticle networks, including honeycomb-like and kagomé networks, provide bending and conductive pathways for concentrating electric fields, which results in the improvement of the permittivity. We envisage that this strategy will open a gateway to prepare hierarchically ordered functional nanocomposites with distinctive dielectric properties.

Modulating Microphase Separation of Lamellae-Forming Diblock Copolymers via Ionic Junctions.

We present a molecular dynamics simulation study investigating the phase behavior of lamellae-forming diblock copolymers with a single ionic junction on the backbone. Our results show qualitative agreement with experimental findings regarding enhanced microphase separation with the introduction of an ionic junction at the conjunction point, while further revealing nonmonotonic changes in domain spacing and order-disorder transition as a function of the electrostatic interaction strength. This highlights the dominant roles of entropic and binding effects of counterions under weak and strong ionic correlations, respectively. The location of the ionic junction is found to effectively modulate the charge distribution and chain conformation in the ordered domains; its presence in the middle of a block promotes folding of the block, leading to a smaller domain size. These findings demonstrate the interplay of ionic coupling with steric hindrance and chain end effects, which enhances our understanding of the delicate control over the microphase domain features.

Symmetric Diblock Copolymers in Cylindrical Confinement: A Way to Chiral Morphologies?

We investigate the confinement-induced formation and stability of helix morphologies in lamella-forming AB diblock copolymers via large-scale, particle-based, single-chain-in-mean-field simulations. Such helix structures are rarely observed in bulk or thin films. Structure formation is induced by quenching incompatibility, χN, from a disordered morphology. If the surfaces of the cylindrical confinement do not prefer one component over the other, we observe that stacked lamellae, with their normals along the cylinder axis, are the preferred morphology. Kinetically, this morphology initially forms close to the cylinder surface, whereas the spontaneous, spinodal microphase separation in the cylinder's interior gives rise to a microemulsion-like morphology, riddled with defects and no directional order. Subsequently, the ordered morphology on the cylinder surface progresses inward, pervading the entire volume. In case that the cylindrical pore is only partially filled, the additional confinement along the cylinder axis generally gives rise to incommensurability between the equilibrium spacing of stacked lamellae and the cylinder height. To accommodate this mismatch, the lamella normals will tilt away from the cylinder axis and generate helices of lamellae on the surface of the cylinder. Again, this order progresses from the cylinder surface inward, generating a chiral morphology. Because the spacing between the internal AB interfaces decreases upon approaching the helix center, the concomitant stress results in a decrease in the number of lamellae and the formation of unique dislocation defects. This type of chiral defect morphology is reproducibly formed by the kinetics of structure formation in partly filled cylindrical pores with nonpreferential surfaces and may find applications in photonic applications.

Rheology of symmetric diblock copolymers

Using large-scale simulations with the graphics processing unit (GPU) accelerated Highly Optimized Object-oriented Many-particle Dynamics (HOOMD)-blue software we investigate the anisotropic, dynamic-mechanical properties of lamellae-forming diblock copolymer melts. Both, the shear-stress autocorrelation function in equilibrium as well as stress-controlled simulations of shear flow are considered. The latter are implemented in (HOOMD)-blue via reverse nonequilibrium molecular dynamics simulation (RNEMDS).We find that copolymer lamellae that are perpendicularly oriented to the shear flow have similar rheological properties than unstructured homopolymer melts. Copolymer lamellae with the metastable parallel and the unstable transverse orientation exhibit similar dynamic-mechanical behavior in the linear regime. Most notably, they are characterized by a high dissipation.(RNEMDS) enables the study of oscillatory shear flow as well as the investigation of nonlinear rheology. Our simulation results for a soft, coarse-grained model at very high frequencies indicate that the finite speed of stress propagation has to be accounted for in the quantitative analysis, and we devise an analytic prediction for the nonlinear velocity and spatially varying stress profiles as a function of the loss and storage moduli.

Kinetics of pattern formation in symmetric diblock copolymer melts.

In equilibrium, copolymers self-assemble into spatially modulated phases with long-range order. When the system is quenched far below the order-disorder transition temperature, however, such an idealized, defect-free structure is difficult to obtain in experiments and simulations, instead a fingerprint-like structure forms. The relaxation toward long-range order is very protracted because it involves numerous thermally activated processes, and the rugged free-energy landscape has been likened to that of glass-forming systems. Using large-scale particle-based simulations of high-aspect-ratio, quasi-two-dimensional systems with periodic boundary condition, we study the kinetics of structure formation in symmetric, lamella-forming diblock copolymers after a quench from the disordered state. We characterize the ordering process by the correlation length of the lamellar structure and its Euler characteristic and observe that the growth of the correlation length and the rate of change of the Euler characteristic significantly slow down in the range of incompatibilities, 15 ≤ χN ≤ 20, studied. The increase of the time scale of ordering is, however, gradual. The density fields of snapshots of the particle-based simulations are used as starting values for self-consistent field theory (SCFT) calculations. The latter converge to the local, metastable minimum of the free-energy basin. This combination of particle-based simulations and SCFT calculations allows us to relate an instantaneous configuration of the particle-based model to a corresponding metastable free-energy minimum of SCFT-the inherent morphology-and we typically observe that a change of a free-energy basin is associated with a change of the Euler characteristic of the particle-based morphology, i.e., changes of free-energy basins are correlated to changes of the domain topology. Subsequently, we employ the string method in conjunction with SCFT to study the minimum free-energy paths (MFEPs) of changes of the domain topology. Since the time scales of relaxing toward the inherent morphology within a free-energy basin and jumps between free-energy basins are not well separated, the MFEP may overestimate the barriers encountered in the course of ordering.

Copolymer Nanocomposite Thin‐Films Under Shear

By means of molecular dynamics simulations, we study the behaviour of lamellae forming diblock copolymer and nanoparticle mixtures in thin‐film geometry under stationary shear. In particular, we investigate the system under transverse mode of shear considering both nonselective and selective types of nanoparticles. We find that the presence of nanoparticles affects the critical shear rate at which the lamellar morphology is not stable during transverse shear and orientation transition sets in. We also study the spatial distribution of nanoparticles in the presence of flow field and its effect on the macroscopic response of the system.

Realizing the Potential of Micro-Phase Separated Block Copolymer Electrolytes: Ion Domain Connectivity Plays a Prominent Role in Ion Conduction

Single ion conducting polymer electrolyte membranes (PEMs) are found at the heart of many electrochemical devices (e.g., fuel cells, flow batteries, electrolyzers, electrodialysis, etc.).(1) The key requirements for such materials include high ionic conductivity, electron insulation, mechanical resilience, selectivity (i.e., high transference #), and chemical, thermal, and mechanical stability.(2, 3) Ionic conductivity is particularly important because it strongly influences the ohmic overpotential in the said electrochemical devices affecting device efficiency.(1, 4) Block copolymer electrolytes represent an attractive set of PEM materials because their micro-phase architecture yields greater ion conduction over their random copolymer counterparts.(5-7) Furthermore, the block copolymer charateristic gives rise to a variety of morphological architectures, while engineering of the block copolymer’s self-assembly influences domain alignment.(8-12) However, there is lack of systematic studies correlating molecular level structural design to bulk material properties like ion transport. In this work, a model lamellae-forming diblock copolymer electrolyte system was manipulated to examine the extent of ion domain connectivity on ion conduction.(13, 14) Careful control of the model system’s volume fraction gave diblock copolymer structures with slightly rich electrolyte domains or slightly rich hydrophobic domains. The slightly rich electrolyte domains had greater contiguous area fraction while simultaneously demonstrating fewer terminal defects. Having a contiguous area fraction from 0.95 to 1.0 resulted in a 2x improvement in ionic conductivity over a non-micro-phase separated block copolymer electrolyte or a micro-phase separated block copolymer electrolyte with poor connectivity. Incremental adjustment in the extent of connectivity revealed an exponential growth curve for ion conductivity as a function of contiguous area fraction. Furthermore, the benefits that a micro-phase separated block copolymer electrolyte affords in terms of ion conductivity were not realized when the block copolymer electrolyte had poor connectivity. The results of this work have far reaching implication into the rationale design of PEM materials based upon block copolymer designs. This talk will emphasize the importance of maximizing ion domain connectivity while taking great strides to minimize terminal defects to boost ion transport in PEM materials. This talk will close with future directions on how molecular level engineering of block copolymer electrolytes offer the potential to reveal how other structural features (e.g., tortuosity(15), grain boundaries(5), and counterion condensation) alter ion transport in PEM materials(16, 17). 1. H. Strathmann et al., Ion-Exchange Membranes in the Chemical Process Industry. Industrial & Engineering Chemistry Research 52, 10364-10379 (2013). 2. H. Strathmann, Ion-Exchange Membrane Separation Processes, Volume 9. Membrane Science and Technology (Elsevier Science, Amsterdam, The Netherlands, 2004), vol. 9. 3. T. Sata, Ion Exchange Membranes: Preparation, Characterization, Modification and Application. (Royal Society of Chemistry, Cambridge, UK, 2004). 4. A. Z. Weber, J. Newman, Modeling Transport in Polymer-Electrolyte Fuel Cells. Chemical Reviews 104, 4679-4726 (2004). 5. Y. A. Elabd, M. A. Hickner, Block Copolymers for Fuel Cells. Macromolecules 44, 1-11 (2011). 6. N. Li, M. D. Guiver, Ion Transport by Nanochannels in Ion-Containing Aromatic Copolymers. Macromolecules 47, 2175-2198 (2014). 7. Y. Schneider et al., Ionic Conduction in Nanostructured Membranes Based on Polymerized Protic Ionic Liquids. Macromolecules 46, 1543-1548 (2013). 8. H. Hu, M. Gopinadhan, C. O. Osuji, Directed self-assembly of block copolymers: a tutorial review of strategies for enabling nanotechnology with soft matter. Soft Matter 10, 3867-3889 (2014). 9. M. Luo, T. H. Epps, III, Directed Block Copolymer Thin Film Self-Assembly: Emerging Trends in Nanopattern Fabrication. Macromolecules 46, 7567-7579 (2013). 10. S. Ji, L. Wan, C.-C. Liu, P. F. Nealey, Directed self-assembly of block copolymers on chemical patterns: A platform for nanofabrication. Progress in Polymer Science, 54-55, 76-127 (2016). 11. S.-J. Jeong et al., Directed self-assembly of block copolymers for next generation nanolithography. Materials Today 16, 468-476 (2013). 12. M. P. Stoykovich, P. F. Nealey, Block copolymers and conventional lithography. Materials Today 9, 20-29 (2006). 13. I. P. Campbell, G. J. Lau, J. L. Feaver, M. P. Stoykovich, Network Connectivity and Long-Range Continuity of Lamellar Morphologies in Block Copolymer Thin Films. Macromolecules 45, 1587-1594 (2012). 14. C. G. Arges, Y. Kambe, H. S. Suh, L. E. Ocola, P. F. Nealey, Perpendicularly Aligned, Anion Conducting Nanochannels in Block Copolymer Electrolyte Films. Chemistry of Materials 28, 1377-1389 (2016). 15. X. Feng et al., Scalable Fabrication of Polymer Membranes with Vertically Aligned 1 nm Pores by Magnetic Field Directed Self-Assembly. ACS Nano 8, 11977-11986 (2014). 16. K. M. Beers, D. T. Hallinan, X. Wang, J. A. Pople, N. P. Balsara, Counterion Condensation in Nafion. Macromolecules 44, 8866-8870 (2011). 17. K. M. Beers, N. P. Balsara, Design of Cluster-free Polymer Electrolyte Membranes and Implications on Proton Conductivity. ACS Macro Letters 1, 1155-1160 (2012). Figure 1

Stress-Induced Solvent Redistribution in Lamellae-Forming Diblock Copolymer Systems

We predict morphology-controlled nanopumping of a nonselective solvent in the swollen lamellae-forming diblock copolymer systems under applied uniaxial deformation of the sample. Normal compression of the lamellae at conditions that the solvent is not extruded (evaporated) from the sample (so-called “sealed” sample) leads to the solvent flow from the lamellar interior to the AB interfaces. On the contrary, the normal expansion results in the increase of the solvent concentration at the interfaces which is practically not accompanied by the solvent flow from the interfaces to the lamellar interior. The physical reason for the nanopumping is shown to be related to the shielding of unfavorable AB contacts of the monomer units at the interface via localization of the solvent molecules. As a result, the solvent concentration at the interface is larger than within the lamellae. Interplay between variation of the interfacial area under the deformation and minimization of their tension is responsible for the solv...

Thermodynamics and Kinetics of Defect Motion and Annihilation in the Self-Assembly of Lamellar Diblock Copolymers

The thermodynamics of dislocations in thin films of lamella-forming diblock copolymers and their climb and glide motions are investigated using single-chain-in-mean-field (SCMF) simulations and self-consistent field theory (SCFT) in conjunction with the string method. The glide motion of a defect perpendicular to the stripe pattern is characterized by large free energy barriers. The barriers not only stem from altering the domain topology; an additional barrier arises from a small-amplitude but long-range domain displacement. In contrast, the climb motion along the stripes does not involve a free energy barrier in accord with the continuous translational invariance along the stripe. Thus, the perpendicular distance (“impact parameter”) between a pair of defects is approximately conserved. Dislocation pairs with opposite Burgers vectors attract each other and move toward each other (“collide”) via climb motion. We find that the forces between apposing defects significantly depend on system size, and the Pe...

Calculations of the free energy of dislocation defects in lamellae forming diblock copolymers using thermodynamic integration

State-of-the-art directed self-assembly (DSA) of block copolymer (BCP) methods still yield defect densities orders of magnitude higher than is necessary in semiconductor fabrication. The defect free energy of a dislocation pair or jog defect, one of the most common defects found in BCP-DSA, is calculated via thermodynamic integration using a coarse-grained molecular dynamics model as a function of χ and the degree of polymerization (N). It is found that χN is not the best predictor of defect free energy and that a single χN value can yield vastly different free energies when χ and N are different. Defect free energy was highly dependent on defect location relative to the underlayer, and free energy differences ∼100 kT were found among the three possible defect locations on a 1:3 guiding pattern. It was found that increasing molar mass dispersity (Ð) significantly reduced defect free energy. Extrapolating from Ð up to 1.5 suggests that the defect will occur in equal proportions to the defect free state at a Ð of around 1.6 for this system. It was found that long chains tended to concentrate near the defect and stabilize the defect.

Small-Angle Neutron Scattering Studies on the Multilamellae Formed by Mixing Lamella-Forming Cationic Diblock Copolymers with Lipids and Their Interaction with DNA.

We demonstrate that the lamella-forming polystyrene-block-poly(N-methyl-4-vinylpyridinium iodine) (PS-b-P4VPQ), with similar sizes of the PS and P4VPQ blocks, can be dispersed in the aqueous solutions by forming lipid/PS-b-P4VPQ multilamellae. Using small-angle neutron scattering (SANS) and 1,2-dipalmitoyl-d62-sn-glycero-3-phosphocholine (d62-DPPC) in D2O, a broad correlation peak is found in the scattering profile that signifies the formation of the loosely ordered d62-DPPC/PS-b-P4VPQ multilamellae. The thicknesses of the hydrophobic and hydrophilic layers of the d62-DPPC/PS-b-P4VPQ multilamellae are close to the PS layer and the condensed brush layer thicknesses as determined from previous neutron reflectometry studies on the PS-b-P4VPQ monolayer at the air-water interface. Such well-dispersed d62-DPPC/PS-b-P4VPQ multilamellae are capable of forming multilamellae with DNA in aqueous solution. It is found that the encapsulation of DNA in the hydrophilic layer of the d62-DPPC/PS-b-P4VPQ multilamellae slightly increases the thickness of the hydrophilic layer. Adding CaCl2 can enhance the DNA adsorption in the hydrophilic brush layer, and it is similar to that observed in the neutron reflectometry study of the DNA adsorption by the PS-b-P4VPQ monolayer.

Short-range ordered photonic structures of lamellae-forming diblock copolymers for excitation-regulated fluorescence enhancement.

Photonic crystals can be represented by periodic nanostructures with alternating refractive indices, which create artificial stop bands with the appearance of colors. In this regard, nanodomains of block copolymers and the corresponding structural colors have been intensively studied in the past. However, the practical application of photonic crystals of block copolymers has been limited to a large degree because of the presence of large defects and grain boundaries in the nanodomains of block copolymers. The present study focuses on the alternative opportunity of short-range ordered nanodomains of block copolymers for fluorescence enhancement, which also has a direct relevance to the development of fluorescence sensors or detectors. The enhancement mechanism was found to be interconnected with the excitation process rather than the alternation of the decay kinetics. In particular, we demonstrate that randomly oriented, but regular grains of lamellae of polystyrene-block-polyisoprene, PS-b-PI, diblock copolymers and their blend with PS homopolymers can behave as Bragg mirrors to induce multiple reflections of the excitation source inside the photonic structures. This process in turn significantly increases the effective absorption of the given fluorophores inside the polymeric photonic structures to amplify the fluorescence signal.

Self-assembly of lamella-forming diblock copolymers confined in nanochannels: Effect of confinement geometry**Project supported by the National Natural Science Foundation of China (Grant Nos. 11204215, 51302187, 20990234, 20925414, 21204040, and 91227121), the Natural Science Foundation of Tianjin City, China (Grant Nos. 12JCYBJC32500 and 14JCZDJC32100), the Program for Changjiang Scholars and Innovative Research Team in University (PCSIRT) (Grant No. IRT1257), and the

The self-assembly of symmetric diblock copolymers confined in the channels of variously shaped cross sections (regular triangles, squares, and ellipses) is investigated using a simulated annealing technique. In the bulk, the studied symmetric diblock copolymers form a lamellar structure with period LL. The geometry and surface property of the confining channels have a large effect on the self-assembled structures and the orientation of the lamellar structures. Stacked perpendicular lamellae with period LL are observed for neutral surfaces regardless of the channel shape and size, but each lamella is in the shape of the corresponding channel's cross section. In the case of triangle-shaped cross sections, stacked parallel lamellae are the majority morphologies for weakly selective surfaces, while morphologies including a triangular-prism-shaped B-cylinder and multiple tridentate lamellae are obtained for strongly selective surfaces. In the cases of square-shaped and ellipse-shaped cross sections, concentric lamellae are the signature morphology for strongly selective surfaces, whereas for weakly selective surfaces, stacked parallel lamellae, and several types of folding lamellae are obtained in the case of square-shaped cross sections, and stacked parallel lamellae are the majority morphologies in the case of ellipse-shaped cross sections when the length of the minor axis is commensurate with the bulk lamellar period. The mean-square end-to-end distance, the average contact number between different species and the surface concentration of the A-monomers are computed to elucidate the mechanisms of the formation of the different morphologies. It is found that the resulting morphology is a consequence of competition among the chain stretching, interfacial energy, and surface energy. Our results suggest that the self-assembled morphology and the orientation of lamellae can be manipulated by the shape, the size, and the surface property of the confining channels.

Polymer‐Coated PtCo Nanoparticles Deposited on Diblock Copolymer Templates: Chemical Selectivity versus Topographical Effects

Metal-polymer hybrid films are prepared by deposition of polymer-coated PtCo nanoparticles onto block copolymer templates. For templating, a thin film of the lamella-forming diblock copolymer poly(styrene-b-methyl methacrylate) P(S-b-MMA) is chemically etched and a topographical surface relief with 3 nm height difference is created. Two types of polymer-grafted PtCo nanoparticles are compared to explore the impact of chemical selectivity versus the topographical effect of the nanotemplate. A preferable wetting of the polystyrene (PS) domains with poly(styrenesulfonate) (PSS)-coated PtCo nanoparticles (instead of residing in the space between the domains) is observed. Our investigation reveals that the interaction between PSS-coated nanoparticles and PS domains dominates over the topographical effects of the polymer surface. In contrast, a non-selective deposition of poly(N-vinyl-2-pyrrolidone) (PVP)-coated PtCo nanoparticles and the formation of large metal-particle aggregates on the film is observed.

Block Copolymer Morphology Formation on Topographically Complex Surfaces: A Self-Consistent Field Theoretical Study

A self-consistent field theoretic study is performed to study morphological development of lamellae-forming diblock copolymers on substrates with a well-defined roughness, modeled as trenches of varying depth and width engraved into the substrates. There are three possible lamellar orientations observed: horizontal lamellae, vertical lamellae that are parallel to the trench direction, and vertical lamellae that are perpendicular to the trench direction. Which of these three morphologies formed depends upon the trench width and surface affinity; however, trench depth has a relatively insignificant effect on the morphological development. Therefore, tuning trench width, but not trench depth, should allow for a reduction of the morphological defect density in directed self-assembly of lamellar morphology of diblock copolymers.

Structural Changes in Lamellar Diblock Copolymer Thin Films upon Swelling in Nonselective Solvents

Using dissipative particle dynamics simulations, we study the swelling of lamellae-forming diblock copolymer films in a nonselective solvent. Both the parallel and the perpendicular orientations of lamellae in the film are studied. The swelling of the film with parallel lamellae is accompanied by an increase of their number. In doing so, the lamellar thickness reveals nonmonotonous behavior: affine growth (low degree of solvent uptake) is succeeded by a decrease in thickness (high degree of solvent uptake). Whereas the first regime reflects a finite size (film thickness) effect, the decrease is a more common effect, which is also valid for perpendicular lamellae, and is due to shrinkage of the diblock copolymers due to the shielding of unfavorable AB contacts by the solvent molecules. The film swelling leads to an increase of the number of perpendicular lamellae as well. However, such an increase is only possible if the film at first is dissolved and then condensed absorbing a certain amount of solvent. O...

Swelling of Block Copolymer Nanoparticles: A Process Combining Deformation and Phase Separation

Swelling of block copolymers is a complex process in which deformation and microphase separation couple together. Here we demonstrated that nanoparticles of block copolymers and polymer composites which have a large variety of phase separation patterns and different shapes can be generated through swelling process. Particularly, we focused on the swelling process of lamellae-forming diblock copolymer nanoparticles and first observed the formation of terrace edges in diblock copolymer nanoparticles as a metastable microstructure in swelling. Moreover, the trace amount of swelling solvent shows a significant influence on the shape of polymer nanoparticles, leading to block copolymer nanodisks and snowman-like composite nanoparticles.

Diblock and triblock copolymer thin films on a substrate with controlled selectivity

Using self-consistent field theory (SCFT), morphology development in symmetric linear ABC triblock copolymer films on neutral and selective substrates has been studied, and it is compared with the triblock copolymer morphologies in bulk. In particular, the effects of the substrate preferable to B (interior) block on nanopattern formation of the copolymer films are of our central interest. Here, we report various nanopatterns with tunable square morphologies. The domain patterns are much more diverse than those parallel to the substrate with substrate selectivity for end-block or those vertical to the substrate without substrate selectivity. Furthermore, in order to figure out an economical and efficient way to fabricate useful passive pattern transfer layers, which have potential applications in microelectronic processes and ultrahigh density storage media, we propose a two-step strategy and scrutinize the conditions for generating square symmetries using cylinder-forming or lamella-forming AB diblock copolymers deposited on substrates created from ABC triblock copolymer films. It is found that a thinner film with weak incompatibility can produce square patterns.

Defectivity in Laterally Confined Lamella-Forming Diblock Copolymers: Thermodynamic and Kinetic Aspects

We use self-consistent field theory (SCFT) to study the directed self-assembly of laterally confined diblock copolymers. In this study, we focus on systems in which the self-assembled lamellae are oriented parallel to selective sidewalls in a channel. While well-ordered, perfect lamellae are observed in narrow channels both experimentally and numerically, undesirable defective structures also emerge. We therefore investigate the energetics of two categories of isolated defects (dislocations and disclinations) for various segregation strengths and channel dimensions, and establish conditions that favor the formation of defects. We also determine the energy barrier and the transition path between defective and perfect states using the string method. We find that only a few kT of energy are necessary to overcome the kinetic barrier and remove a defect, sharply contrasting with the large gain in free energy (many tens of kT) that is necessary for the formation of a defect from the pristine state.

Mediating polymer crystal orientation using nanotemplates from block copolymer microdomains and anodic aluminium oxide nanochannels

Crystals formed by polymers are typically nanoscale in at least one dimension. The directional control of properties via precise control of the orientations of polymer nanocrystals has strong relevance to technical applications in various areas. Polymer crystals may exhibit preferential orientation when they are formed inside nanoscale domains or pores. Such a confinement-mediated orientation behavior has been a subject of extensive investigation over the past two decades, where a block copolymer in which two or more chemically different sub-chains form a single molecule template system that has received the most attention. In this article, we focus on an overview of the orientation behavior of polymer crystals under the influence of one-dimensional (1-D) and two-dimensional (2-D) confinement templated by the lamellar and cylindrical microdomains of block copolymers, respectively. In the case of lamellae-forming diblock copolymers, both the crystalline–amorphous system (which is composed of one type of nanocrystals) and the more complex double-crystalline diblock (which consists of two types of nanocrystals) are considered. In addition to the templates offered by block copolymers, the preferential orientation of polymer crystals confined in the inorganic anodic aluminium oxide (AAO) nanochannels has also been critically reviewed due to strong relevance to the 2-D confinement effect. Moreover, the significant thermodynamic and kinetic factors governing the crystal orientation behavior have been summarized, which may allow one to understand the strategy for tuning the preferential orientation of polymer nanocrystals under the spatial confinement of different dimensionalities.