SUPERCRITICAL IMPREGNATION OF ACTIVE PRINCIPLES INTO/ONTO POLYMERIC MATRICES

THE RISING DEMAND FOR SUSTAINABLE AND INTENSIFIED INDUSTRIAL PRODUCTION HAS DRIVEN THE SEARCH FOR ENVIRONMENTALLY FRIENDLY TECHNOLOGIES. IN THIS CONTEXT, SUPERCRITICAL CO₂ (SCCO₂) OFFERS A PROMISING ALTERNATIVE TO CONVENTIONAL ORGANIC SOLVENTS FOR THE IMPREGNATION-BASED MODIFICATION AND FUNCTIONALIZATION OF MATERIALS. OVER THE PAST DECADE, SUPERCRITICAL FLUID IMPREGNATION (SFI) HAS EMERGED AS A VALID ALTERNATIVE TO TRADITIONAL METHODS, UTILIZING SUPERCRITICAL CARBON DIOXIDE TO INTRODUCE ACTIVE SUBSTANCES INTO TARGETED MATERIALS. ITS POTENTIAL EXTENDS TO FIELDS SUCH AS PHARMACEUTICALS, ENVIRONMENTAL PROTECTION, AND POLLUTION CONTROL DEVICES. THIS THESIS EXAMINES AND IMPROVES THE USE OF SUPERCRITICAL CO₂ FOR DELIVERING AND IMPREGNATING MOLECULES, FOCUSING ON KEY PHENOMENA THAT AFFECT LOADING EFFICIENCY AND PENETRATION DEPTH. THE RESEARCH ENCOMPASSES VARIOUS MATERIAL SYSTEMS IMPREGNATED WITH SUPERCRITICAL CO₂ FOR APPLICATIONS SUCH AS FOOD PACKAGING, REDUCTION OF VOLATILE ORGANIC COMPOUNDS IN WASTE STREAMS, AND PHARMACEUTICALS. IT INVOLVES ADJUSTING PROCESS PARAMETERS TO UNDERSTAND BETTER THE THERMODYNAMIC AND TRANSPORT MECHANISMS THAT INFLUENCE IMPREGNATION OUTCOMES. IN ADDITION, THIS THESIS PRESENTS A NOVEL PROCESS FOR EMBEDDING ACTIVE COMPOUNDS INTO POLYMER MATRICES, THEREBY SIGNIFICANTLY ENHANCING DRUG LOADING BY LEVERAGING THE UNIQUE PROPERTIES OF SUPERCRITICAL CO2. THE STRATEGY INVOLVES USING STEARIC ACID (SA) AS A POROGEN IN THE POLYMERIC MATERIALS. POLYMER STRUCTURES WITH THESE POROGENS GO THROUGH A NOVEL, ONE-STEP PROCESS CALLED SUPERCRITICAL LEACHING AND IMPREGNATION (SLIM). IN SLIM, THE POROGEN IS ELIMINATED SIMULTANEOUSLY WITH THE IMPREGNATION OF THE DRUG, SIGNIFICANTLY BOOSTING IMPREGNATION EFFICIENCY. THIS PROCESS YIELDS A TAILORED POROUS STRUCTURE THAT INFLUENCES DIFFUSION MECHANISMS AND ENHANCES ACCESS TO ACTIVE SITES, IMPROVING THE POLYMERS' FINAL PROPERTIES. THE EFFICACY OF THIS APPROACH WAS DEMONSTRATED ACROSS VARIOUS POLYMERIC STRUCTURES, INCLUDING ELECTROSPUN MEMBRANES AND MELT-COMPOUNDED FILAMENTS, FOR THE SUBSEQUENT MANUFACTURING OF MICRO-NEEDLE PATCHES BY COMPRESSION MOLDING. IN THE CASE OF ELECTROSPUN MEMBRANES, KINETIC STUDIES AT 20 MPA SHOW THAT LONGER CONTACT TIMES LEAD TO INCREASED DRUG LOADINGS, REACHING UP TO 22.4% WACYCLOVIR/WPOLYMER AT 50°C. WITHOUT A POROGEN, THE ACYCLOVIR (THE MODEL DRUG USED FOR THE EXPERIMENTATION) LOADING WAS 1.6%. INCORPORATING A SUITABLE POROGEN INTO THE SLIM PROCESS ENABLES THE FABRICATION OF STRUCTURES WITH CONTROLLED PORE SIZES, THEREBY FACILITATING TRANSPORT PHENOMENA AND ENSURING HIGH DRUG LOADING. THE EFFICACY OF THIS NEW STRATEGY WAS ALSO TESTED ON EXTRUDED POLYLACTIC ACID (PLA)-SA FILAMENT, WHICH IS HELPFUL FOR POST-APPLICATION IN OTHER POLYMER MANUFACTURING PROCESSES. FOR EXAMPLE, WHEN A MICRONEEDLE PATCH WAS FORMED FROM A CONTINUOUS STRUCTURE, A POROUS STRUCTURE WAS CREATED, WITH PORES WHOSE AVERAGE DIAMETER DEPENDED ON THE INITIAL STEARIC ACID CONCENTRATION AND THE TEST CONDITIONS. THE RESEARCH ELUCIDATES THE MECHANISMS OF IMPREGNATION AND ESTABLISHES A FOUNDATION FOR A NEW PROCESS THAT EMPHASIZES THE INTERACTION BETWEEN SUPERCRITICAL CO₂ AND MATERIALS. THIS OFFERS FUNDAMENTAL INSIGHTS FOR DEVELOPING SUSTAINABLE AND SCALABLE METHODS APPLICABLE ACROSS DIFFERENT INDUSTRIES.