Engineered Porosity in Microcrystalline Diamond-Reinforced PLLA Composites - Effects of Particle Concentration on Thermal and Structural Properties

At a Glance

Metadata	Details
Publication Date	2025-10-04
Journal	Materials
Authors	Mateusz Ficek, Franciszek Skiba, Marcin Gnyba, Gabriel Strugała, Dominika Ferneza
Institutions	Gdańsk University of Technology, Wrocław University of Science and Technology
Analysis	Full AI Review Included

Technical Documentation & Analysis: Microcrystalline Diamond-Reinforced PLLA Composites

Executive Summary

This research validates the use of microcrystalline diamond particles (MDPs) as a functional filler in biodegradable poly(L-lactic acid) (PLLA) matrices, achieving engineered porosity for advanced applications.

Engineered Porosity: Systematic control of composite porosity was achieved, ranging from 11.4% to 32.8%, dependent on diamond particle size (0.125 µm and 1.00 µm) and concentration (5 to 75 wt%).
Structural Transition: X-ray computed microtomography (µCT) confirmed a controllable transition from large-volume interconnected pores to numerous small-volume closed pores with increasing diamond content.
Purely Physical Interaction: Spectroscopic analysis (Raman, FTIR) confirmed successful diamond incorporation with purely physical interactions, maintaining the characteristic diamond lattice vibration at 1332 cm^-1 without chemical bonding.
Thermal Modification: Diamond incorporation significantly modified PLLA crystallization behavior, evidenced by a decrease in melting temperature from 181 °C (neat PLLA) down to 172 °C (75 wt% MDP125 loading).
High-Value Applications: The resulting multi-hierarchical structures are highly relevant for high-performance biodegradable materials required in tissue engineering scaffolds, specialized filtration technologies, and thermal management systems.
Material Relevance: The study utilizes HPHT microcrystalline diamond, confirming the viability of high-thermal-conductivity diamond fillers—a core capability of 6CCVD’s MPCVD Polycrystalline Diamond (PCD) products.

Technical Specifications

Parameter	Value	Unit	Context
Diamond Particle Size (Small, D50)	0.125	µm	Used for PLLA/MDP125 series
Diamond Particle Size (Large, D50)	1.00	µm	Used for PLLA/MDP1000 series
Diamond Concentration Range	5 to 75	wt%	Tested concentration range
Achieved Porosity Range	11.4 to 32.8	%	Controllable porosity via concentration
Lowest Porosity Recorded	7	%	Anomalous result at 5 wt% MDP1000
Characteristic Diamond Peak	1332	cm^-1	Raman lattice oscillation confirmation
Neat PLLA Melting Temperature	180 to 181	°C	DSC analysis, second heating scan
Lowest Melting Temperature	172	°C	Observed at 75 wt% MDP125 loading
Melting Enthalpy Reduction	46 to 14.5	J/g	Reduction observed for 75 wt% MDP125
Diamond Thermal Conductivity (Reference)	~2200	W·m^-1·K^-1	High thermal property driving degradation
µCT Voxel Resolution	19.64	µm	Used for 3D spatial porosity analysis

Key Methodologies

The PLLA/MDP composites were fabricated using the Thermally Induced Phase Separation (TIPS) technique, specifically employing freeze-drying (lyophilization) to control porosity and structure.

Solution Preparation: Poly(L-lactide) (PLLA) was dissolved in 1,4-dioxane to create a 2.5 wt% solution.
Filler Incorporation: HPHT diamond microparticles (MDPs) of two sizes (0.125 µm and 1.00 µm) were added to the PLLA solution at precise weight ratios (5 wt% to 75 wt%).
Homogenization: The suspension was stirred for 24 hours at 60 °C (500 rpm) to ensure uniform dispersion of the diamond filler.
Molding and Freezing: 1 mL aliquots were poured into 24-well plates and frozen for 24 hours at -20 °C.
Lyophilization: Samples underwent freeze-drying for 24 hours at a temperature of -50 °C and a pressure of approximately 20 Pa, resulting in highly porous foam composites.
Structural Characterization:
- Morphology: Scanning Electron Microscopy (SEM) was used to examine cross-sections and surface coverage.
- Porosity: X-ray computed microtomography (µCT) provided 3D spatial porosity analysis and pore size distribution.
- Bonding: ATR-FTIR and Raman spectroscopy confirmed the absence of chemical bonding and the presence of the diamond lattice.
Thermal Characterization: Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) were used to assess crystallization behavior, melting points, and thermal stability (T-5%, Td, Td,max).

6CCVD Solutions & Capabilities

The successful integration of microcrystalline diamond into polymer matrices for enhanced thermal and structural control aligns perfectly with 6CCVD’s expertise in high-quality MPCVD diamond materials. This research highlights a critical need for reliable, high-purity diamond fillers and substrates in advanced thermal management and biomedical applications.

Applicable Materials for Replication and Extension

To replicate or extend this research, particularly in scaling up thermal management systems or creating robust filtration membranes, 6CCVD recommends the following materials:

6CCVD Material	Recommended Grade	Application Relevance
Polycrystalline Diamond (PCD)	Thermal Grade (High Purity)	Ideal for replicating the microcrystalline structure used in the paper, offering superior thermal conductivity (up to 2000 W·m^-1·K^-1) in a robust, scalable wafer format.
Single Crystal Diamond (SCD)	Optical or Electronic Grade	For high-precision applications requiring ultra-low defect density or specific crystal orientation, such as high-power thermal spreaders integrated into the composite.
Boron-Doped Diamond (BDD)	Heavy or Light Doping	Essential for extending the research into electrochemically active tissue scaffolds or specialized filtration membranes requiring enhanced redox kinetics (as referenced in related literature [16]).
Custom Diamond Powder	Microcrystalline/Nanocrystalline	6CCVD can supply high-purity MPCVD diamond powder tailored to specific size distributions (e.g., 0.1 µm to 1.0 µm) for precise replication of the composite filler.

Customization Potential for Advanced Composites

The paper emphasizes the need for controlled particle size, uniform dispersion, and potential surface functionalization to optimize interfacial compatibility. 6CCVD offers comprehensive customization services to meet these advanced requirements:

Custom Dimensions and Thickness: We provide PCD plates/wafers up to 125mm in diameter, allowing researchers to scale up the fabrication of large-area filtration membranes or tissue scaffolds far beyond the 24-well plate scale used in the study.
Precision Polishing: While the paper used powder, if the composite requires integration with a diamond substrate (e.g., for heat sinking), 6CCVD offers ultra-smooth polishing (Ra < 5nm for inch-size PCD) to minimize interfacial thermal resistance.
Custom Metalization: For thermal management systems where the diamond composite must interface with electronics, 6CCVD provides in-house metalization services, including Ti, Pt, Au, Pd, W, and Cu layers, enabling low-resistance thermal and electrical contacts.
Laser Cutting and Shaping: We offer precision laser cutting services to create custom geometries and complex shapes required for hierarchical structures, filtration channels, or specialized tissue engineering scaffolds.

Engineering Support

The successful fabrication of these multi-hierarchical structures relies heavily on optimizing the diamond filler morphology and surface chemistry. 6CCVD’s in-house PhD team specializes in diamond surface modification and material selection for complex systems.

Interfacial Optimization: We can assist researchers in selecting the optimal diamond surface termination (e.g., hydroxyl-terminated surfaces mentioned in the discussion) and morphology to enhance interfacial bonding and control void nucleation kinetics, crucial for reproducible porosity control in Tissue Engineering Scaffolds and Thermal Management Systems.
Process Validation: Our team provides consultation on how MPCVD diamond properties (purity, defect density) influence crystallization kinetics and foam morphology across various polymer matrices and solvents, ensuring reproducible manufacturing outcomes.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

This research explores microcrystalline diamond particles in poly(L-lactic acid) matrices to create structured porous composites for advanced biodegradable materials. While nanodiamond-polymer composites are well-documented, microcrystalline diamond particles remain unexplored for controlling hierarchical porosity in systems required by tissue engineering, thermal management, and filtration industries. We investigate diamond-polymer composites with concentrations from 5 to 75 wt% using freeze-drying methodology, employing two particle sizes: 0.125 μm and 1.00 μm diameter particles. Systematic porosity control ranges from 11.4% to 32.8%, with smaller particles demonstrating reduction from 27.3% at 5 wt% to 11.4% at 75 wt% loading. Characterization through infrared spectroscopy, X-ray computed microtomography, and Raman analysis confirms purely physical diamond-polymer interactions without chemical bonding, validated by characteristic diamond lattice vibrations at 1332 cm−1. Thermal analysis reveals modified crystallization behavior with decreased melting temperatures from 180 to 181 °C to 172 °C. The investigation demonstrates a controllable transition from large-volume interconnected pores to numerous small-volume closed pores with increasing diamond content. These composites provide a quantitative framework for designing hierarchical structures applicable to tissue engineering scaffolds, thermal management systems, and specialized filtration technologies requiring biodegradable materials with engineered porosity and enhanced thermal conductivity.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma18194606

References

2024 - Applications of diamond films: A review [Crossref]
2012 - The mechanical and strength properties of diamond [Crossref]
2024 - Diamond Nanostructures at Different Dimensions: Synthesis and Applications [Crossref]
2021 - Nanodiamond-Based Fibrous Composites: A Review of Fabrication Methods, Properties, and Applications [Crossref]
2014 - Preparation and Properties of Nanodiamond/Poly(Lactic Acid) Composite Nanofiber Scaffolds [Crossref]
2010 - Nanodiamond/Poly (Lactic Acid) Nanocomposites: Effect of Nanodiamond on Structure and Properties of Poly (Lactic Acid) [Crossref]
2024 - Effect of Curcumin-Modified Nanodiamonds on Properties of Eco-Friendly Polylactic Acid Composite Films [Crossref]
2023 - Effect of Functionalized Nanodiamond on Properties of Polylactic Acid Eco-Friendly Composite Films [Crossref]
2018 - Microdiamond/PLA Composites with Enhanced Thermal Conductivity through Improving Filler/Matrix Interface Compatibility [Crossref]